Debt could rise to more than 300% of the size of the economy by 2070, the government's forecaster says.
The UK 's public debt could soar as the population ages and tax receipts fall, the government's independent forecaster has warned.
The Office for Budget Responsibility said debt could rise to more than 300% of the size of the economy by 2070, up from around 100% currently.
Climate change and geopolitical tensions also posed "significant" risks to government finances, it added.
But it called current government plans to reduce debt "relatively modest".
Public debt is the stockpile of money borrowed by the government over the years to fund its spending.
Chancellor Jeremy Hunt has set a target of getting underlying debt to fall in five years' time.