The Debt-as-Real-Cost Lens
Debt interest is a tax today, not a problem for grandchildren
The conventional political framing of public debt treats it as a problem for future generations — a moral claim about what we owe our grandchildren. Helen Miller argues this framing is dangerously misleading because it hides the real, immediate cost: debt interest that must be paid today, crowding out spending on hospitals, schools, and infrastructure.
The UK moved from spending a few tens of billions per year on debt interest to over £100 billion — not in a generation, but in a few years following the pandemic and the sharp rise in interest rates. That £100 billion must first be raised in taxes before anything useful can be funded. Every pound going to debt servicing is a pound that cannot go to a nurse or a teacher. This reframes the question from 'are we saddling our grandchildren?' to 'what are we not funding right now because of past borrowing?'
The lens also clarifies the borrowing debate. Miller distinguishes between productive borrowing — infrastructure investment that generates future returns — and consumption borrowing, used for wages or benefits that are consumed immediately. The case for the latter is much weaker. Applying this lens, the question is never just 'can we afford to borrow more?' but 'what does that borrowing cost us each year in forgone services, and is the thing we are borrowing for worth that price?'
- Debt interest is a present tax, not a deferred burden — it crowds out services today.
- Borrowing for investment that generates future returns is qualitatively different from borrowing to pay wages or benefits.
- The correct question is not 'can we borrow more?' but 'what does each additional pound of debt cost us per year in forgone spending?'
- High revenues and squeezed services are compatible when debt servicing consumes a large share of those revenues.
- Fiscal headroom is a misleading concept unless paired with a full account of borrowing's annual real cost.
- Identify the debt servicing bill in absolute termsBefore assessing any fiscal situation, find out how much the government is spending annually on debt interest. This is the floor cost that must be covered before any service is funded. In the UK that figure exceeded £100bn — context that transforms how you read every budget.Pro tipFrame the number as a proportion of total tax revenues, not just as a standalone figure. £100bn out of £1,100bn collected tells you roughly 9p in every pound goes to interest before services.WarningDon't confuse 'the debt is high' with 'the debt is costing us a lot right now.' The cost depends on the interest rate and the maturity profile of existing debt.
- Classify the borrowing by typeSeparate proposed or existing borrowing into productive investment (infrastructure, education) versus consumption spending (wages, benefits, day-to-day costs). The economic case for each is radically different and should be evaluated separately.Pro tipAsk: will this spending generate a future return that helps repay the debt, or is it consumed now? If the latter, the full interest cost is a net drag with no offsetting benefit.
- Reframe the fiscal debate from headroom to opportunity costWhen politicians or commentators ask 'does the government have headroom?', reframe: 'what is the annual cost of using that headroom, and what service does it displace?' This converts abstract fiscal space into concrete trade-offs that citizens can evaluate.Pro tipConnect to visible service quality: the £100bn on debt interest is roughly equivalent to the entire NHS capital budget many times over. Concrete comparisons land better than percentages.
- Track the 5-year horizon ratchetReview the OBR's Fiscal Sustainability Report chart showing that governments repeatedly promise debt will fall in five years — and repeatedly fail to deliver. Use this as a base-rate check: optimistic future projections should be discounted heavily given the historical pattern.Pro tipMiller's 'eating cake today, exercising tomorrow' framing is useful for communicating this to non-technical audiences.WarningDon't use historical failure rates to argue borrowing is always bad — use them to calibrate appropriate skepticism about any specific forecast.
In just a few years following the pandemic and the 2022 rate cycle, UK annual debt interest payments moved from a few tens of billions to over £100bn. Meanwhile the government was collecting record-high tax revenues yet public services were visibly struggling.
The OBR's Fiscal Sustainability Report charted decades of governments promising that debt would start falling in the next five years. The chart shows the forecast horizon continuously rolling forward, with debt never actually falling as promised.
When Labour increased investment borrowing in their spending review, a large share went to net zero and defence — not the most growth-generating categories. A smaller share went to housing, transport and science.
Miller developed this framing through IFS research on UK fiscal sustainability, particularly as debt servicing costs accelerated following the 2022 interest rate cycle. She has used it repeatedly to push back on the political debate, which she argues has become fixated on the wrong question — whether the government has 'fiscal headroom' — rather than on the real cost of expanding the debt stock. The shift from abstract future burden to concrete present drain is her core communication move.