Burnham vs. bonds: Gilt risks are skewed to the downside

Andy Burnham is set to become UK Prime Minister unopposed from within his own Labour Party, but he may face tougher opposition in the form of the bond market.

Investors will not forget that only last year, Burnham was saying the UK needed to "get beyond this thing of being in hock to the bond markets." On 29 June 2026, in his first major speech as prime minister-in-waiting, he tied his entire programme to "the discipline of our current fiscal rules," the framework built specifically to reassure the creditors he once promised to escape.

Does this shift in language show Burnham views the bond market as a partner to be managed in delivering his vision? Or could it be a temporary soothing of an opponent whose bluff he plans to call?

Gilts’ underlying vulnerability remains

Investors should not be lulled into a false sense of security by the rally in Gilts since 10-year yields hit their highest level since the global financial crisis in mid-May. Several things have gone right for Gilts since. UK inflation data came in below expectations, energy price pressure has eased with the tentative deal between the US and Iran, and much political uncertainty has been removed thanks to Burnham’s lack of challengers. None of this removes the underlying vulnerabilities which have made Gilt yields more sensitive to shocks than other developed market government bonds over the last two years, and in our view will continue to do so.

Burnham inherits a debt-to-GDP ratio of close to 100% and the UK’s gross debt issuance remains among the heaviest in the G7. The Gilt buyer base has been transformed. Defined benefit pension schemes, once the captive bid at the long end, are selling to insurers through buyouts. The Bank of England (BoE) is handing duration back to the market through quantitative tightening. Hedge funds account for roughly 60% of Gilt trading volume. Foreign investors take more than a quarter of new issuance. 

All of which means the marginal buyer of Gilts is now more price sensitive. A lack of fiscal headroom does not reassure those buyers. At its last forecast in November 2025, the Office for Budget Responsibility (OBR) gave the government a 59% probability of achieving a current budget surplus (meeting the fiscal rule) by 2029/30, hardly an overwhelming margin of safety. Higher inflation can raise welfare spending, departmental budgets and index-linked debt costs. Weaker growth reduces tax receipts. These pressures also interact with each other. Higher Gilt yields increase debt interest costs, which worsens the fiscal arithmetic, which reduces headroom, which makes investors more nervous about future borrowing, which can push yields higher again. This leaves Burnham’s plans hostage to growth and inflation.

Does pro-growth mean pro-borrowing?

Burnham’s pitch is explicitly pro-growth, but judging any growth impact on Gilt demand is virtually impossible given the lack of a concrete policy platform. Which of the floated policies will go through, how effectively they will be executed, how they interact with reality over time, and the timing of market perceptions of their costs and benefits will all matter. Our strongest prediction at this stage is that most measures will be much smaller scale than their headline ambitions. 

For example, what has been called the biggest council house building programme since the post-war period will reportedly be financed by redirecting the existing £39bn Affordable Homes Programme rather than new money.  At current build costs of roughly £250,000 per home, £3.9bn a year delivers perhaps 15,000 homes; the post-war programmes Burnham references built over 200,000 a year. A serious housebuilding and planning reform agenda could improve the supply side of the economy, but it is slow and a redirection of existing funds is marginal to the Gilt market. 

Greater devolution from Westminster may bring the UK more in line with the rest of the G10, but whether it can help reduce the regional productivity gap with London is much debated, and even the most optimistic reading puts the potential gains beyond the time horizon both the OBR and Gilt investors use to judge the UK’s fiscal position.

Reindustrialisation is another long-dated bet. Defence, energy, manufacturing and regional investment may all be politically attractive, and some may be economically justified. But industrial strategy has a mixed record, and the gains are usually uncertain, capital-intensive and slow. The market will quickly distinguish between policy that crowds in private capital and policy that requires permanent public subsidy.

Public ownership is the clearest growth risk. Burnham’s supporters may argue that water, rail, energy and other essential services need a more interventionist model, and there may be sound political and consumer arguments for it. But from a Gilt market perspective, the concern is not only the direct fiscal cost. Leaning more on intervention than full public ownership may avoid vast borrowing needs, but it still sends a costly signal to private capital in regulated sectors. If investors conclude that returns in utilities, infrastructure or energy networks are more exposed to political intervention, the required return on UK investment will rise. That is a growth problem before it is a bond market problem. 

Tax a tempting target

We predict the ultimate scale of reforms to be small because the existing fiscal rules limit the scope for borrowing and the growth wager have to be funded. Burnham already faces several spending requirements outside of his growth agenda. The recently unveiled Defence Investment Plan, for example, as well as previous commitments on social care, public sector pay and welfare extension.

Burnham has said he will stick to Labour’s manifesto pledge not to raise income tax, national insurance or VAT, but that there is “some room” for movement on tax. The UK tax burden is already historically high by domestic standards, with tax revenue as a share of national income set to reach a UK record of 37.4% in 2026/27 according to the Institute for Fiscal Studies.

Burnham's stated instinct is to shift taxation from income to wealth. The growth impact depends almost entirely on which kind. His most developed thinking is on land, in the form of a long-advocated land value tax with a proportional property tax to replace council tax and stamp duty. The first-order behavioural effects are positive. Land does not move, taxing it penalises hoarding rather than investment, and abolishing stamp duty could remove a genuine drag on labour mobility.

However, the people around Burnham appear drawn to capital: Louise Haigh, a key figure in his team has called for aligning capital gains tax (CGT) with income tax and ending the CGT uplift on death. Capital taxes deter the marginal investment and the marginal entrepreneur, against a burden already at a post-war high. Wealth-adjacent taxes have a similar problem. They are politically attractive because they appear to raise money from narrow, affluent bases. But narrow bases can be mobile, quick to adapt and difficult to value. The more targeted the measure, the more likely it is that the OBR will apply behavioural discounts.

Tax rises could be positive for Gilts if they are seen to reduce borrowing in a way the OBR regards as credible, and investors may welcome them. But fiscal arithmetic and economic impact can act in different directions. A tax rise can improve the deficit forecast while weakening the growth base on which future revenues depend. 

Choice of Chancellor a key signal

The potential growth-positive elements of Burnham’s likely agenda – housing, skills clusters, land taxation – are slow-acting and largely invisible to the OBR's forecasts. The growth-negative elements – ownership uncertainty, capital taxation, safeguarding specific industries – act immediately. The costs are frontloaded and the benefits backloaded: the exact mirror of his fiscal problem.

Over the three-to-five-year timescale on which the fiscal rules bind and on which Gilt investors tend to price fiscal risk, we think the market will conclude Burnham’s policy programme nets mildly negative. But geopolitical events can clearly quickly overtake domestic tweaks. It is how the market believes Burnham’s administration will react to these events which matters most. If the fiscal headroom is eaten up, will spending be cut back or will the fiscal rules be abandoned?

Burnham’s first big market test is his choice of Chancellor. Does he buy credibility cheaply, or does he choose to test it? The Gilt market does not want Ed Miliband, who is perceived as more interventionist and ideological than pro-business or growth. A more market-friendly appointment would reassure investors that Burnham understands the constraint, without requiring a single policy concession.

One risk perhaps being underestimated is the possibility of a Burnham government seeking to change the remit of the institutions that make up the UK’s fiscal infrastructure, such as the Treasury, the OBR and the BoE. Any sense that they are being marginalised, bypassed or treated as obstacles could do more damage than any individual policy announcement.

Burnham has reportedly ruled out one proposal of splitting the Treasury, preserving a powerful fiscal gatekeeper. However, we worry arguments about diluting the BoE’s inflation focus may gain momentum. While the US Federal Reserve successfully operates a dual mandate, it does so from a position of entrenched credibility. Gilt investors will also carefully scrutinise any reinterpretation or “gaming” of the fiscal rules. The market may allow some flexibility around timing, investment and forecast uncertainty, provided the OBR process is respected and the debt path remains credible. But the tolerance is narrow and will be a function of accumulated credibility.

Risks skewed to downside for Gilts

We see Burnham's pre-emptive surrender to the fiscal rules as evidence that the institutional memory of Liz Truss's “mini-Budget” fiasco in 2022 continues to impose discipline on politicians. Burnham does not need to launch spending cuts to reassure the Gilt market, but he must indicate, between his Chancellor appointment and the November Budget, that his growth agenda amounts to more than higher taxes funding a larger state. We do not predict any missteps of that magnitude, nor corresponding Gilt spikes. However, after a period in which positive news flow has suppressed Gilt volatility, we think the risks are skewed to the downside as Burnham begins his premiership. That leaves the long end of the Gilt market vulnerable.

It may not take a crisis for bond investors to reprice UK fiscal risk; it may only take the market concluding that discipline is being stretched rather than observed. All the political pressure Burnham faces will push him to seek additional borrowing. With so many avenues through which the new prime minister could seek fiscal flexibility, we think he will be tempted to probe the limits of the Gilt market’s tolerance.