The UK’s Office for Budget Responsibility (OBR) has warned that the UK Government should take early action to prevent its debt from moving onto an “unsustainable and ever-rising path.”

The UK’s official forecaster predicted that long-term population changes and economic trends will put pressure on government spending.

The OBR warnings came in its latest annual fiscal risks and sustainability report.

The UK has experienced one of the largest increases in government debt of any advanced economy over the past two decades, the OBR said.

It said primary UK government spending, excluding debt interest, is projected to rise from 40% of gross domestic product (GDP) in 2030-2031 to 49% by 2075-2076, according to its baseline scenario.

In June, the UK’s Office for National Statistics (ONS) said the UK’s public sector net debt excluding public sector banks (PSND-ex) has reached £2.984 trillion — about 95.1% of GDP.

“In nearly all of the scenarios we explore, debt eventually moves onto an unsustainable and ever-rising path,” said the OBR in the report.

“We stress that it is not plausible that the UK, or any other country, could remain on any of the unsustainable paths set out in these scenarios, because they imply that debt will ultimately grow explosively …”

The report warned: “The degree of tightening required to prevent debt from following an unsustainable path increases if it is delayed to future years.

“This would make it more costly and place more of a burden on future generations.”

A spokesman for HM Treasury said: “We have the right economic plan to deal with economic shocks.

“Our plan to reduce the deficit has been endorsed by the IMF (International Monetary Fund) and the OBR forecast that it will fall every year this parliament, meaning we will be borrowing less than the G7 average.

“This Government has remained committed to protecting households and businesses through providing economic stability via our non-negotiable fiscal rules while protecting over a £120 billion increase in capital spending.”