The bleakest estimates project debt to surpass 300 per cent of GDP in the next 50 years.

To prevent further climbing of public debt, and bring it back to a sustainable level of 75 per cent, the OBR suggests that either public spending should be reduced, taxation increased, or both.

The OBR cites the combination of “ageing and other domestic cost pressures” as factors that have pushed public debt towards an unsustainable course. “a global financial crisis, a global health crisis” and most recently a “global energy crisis” are all factors that have shocked and strained the economy.

The report goes more in-depth on these threats:

• Rising geopolitical tensions (Chapter 2). The Russian invasion of Ukraine has prompted many to reassess the risks from both conventional and cyber security threats and the sustainability of current historically low levels of defence spending across Western countries. Rising geopolitical tensions have also manifested themselves in the economic sphere with the breakdown of multilateral trade negotiations, the US-China tariff war, and a slowdown, and partial reversal, in international trade and investment flows potentially auguring a retreat from the global economic integration that has brought significant economic gains over the past 70 years.
• Higher energy prices (Chapter 3). The recent more than doubling of gas and oil prices and the rise in inflation to rates not seen since the energy crises of the 1970s have underscored the economic and fiscal risks associated with the UK’s continued dependence on fossil fuel imports. It has also brought into sharper focus the fiscal choices and trade-offs involved in shifting the UK’s energy mix to one that is compatible with getting to net zero emissions by 2050.
• Long-term fiscal pressures (Chapter 4). The pandemic has had remarkably little impact on the medium-term fiscal position (with debt marginally higher but the primary balance slightly stronger), thanks in part to the substantial tax rises announced in its wake. Since our 2018 FSR, demographic pressures have eased somewhat in the near-term thanks to a lower birth rate and slower improvements in life expectancy, reducing age-related spending as a share of GDP, while lower migration levels bring some fiscal offsets. But in the long run the pressures of an aging population on spending and the loss of existing motoring taxes in a decarbonising economy leaves public debt on an unsustainable path in the long term.