Government running costs will be cut by 15% by the end of the decade, the chancellor has promised.

Rachel Reeves told the BBC savings would be made from back office and administrative roles rather than front-line services.

But unions warned the impact of cuts would still be felt by the public.

It comes ahead of the chancellor’s Spring Statement on Wednesday, when she is expected to announce spending cuts for some government departments.

The move is part of an ongoing spending review looking into all areas of government activity.

In the coming week, Whitehall departments will receive a letter from Cabinet Office Minister Pat McFadden with instructions to make savings amounting to more than £2bn a year by the end of the decade.

Sectors such as human resources, policy advice, communications and office management are expected to be in the firing line.

Reeves told the BBC’s Sunday with Laura Kuenssberg programme the government wanted to use savings to invest in its priorities, such as the NHS.

She said the size of the Civil Service had increased “massively” during Covid and had not returned to pre-pandemic levels.

Reeves added that cutting running costs by 15% was “more than possible” given advances in technology and artificial intelligence.

Pressed over how many civil service jobs could go, the chancellor told Sky News she was “confident” numbers could be reduced by 10,000.

As of December 2024, an estimated 547,735 people were employed by the Civil Service according to the Office for National Statistics. This includes temporary and casual employees.

Civil servants are politically impartial officials employed by the government, covering areas including policy development and services like benefits and prisons.

Dave Penman, head of the FDA union, which represents senior civil servants, said the distinction between back office and the front line was “artificial”.

“The idea that cuts of this scale can be delivered by cutting HR and comms teams is for the birds,” he said.

“This plan will require ministers to be honest with the public and their civil servants about the impact this will have on public services.”

Meanwhile, Mike Clancy, head of the Prospect union, said: “Civil servants in all types of roles help the public and deliver the government’s missions.

“Cutting them will inevitably have an impact that will be noticed by the public.”

Earlier this month Cabinet Office Minister McFadden promised “radical” reform of the Civil Service, with performance-related pay for senior officials and those not meeting expectations incentivised to leave their jobs.

And last week Prime Minister Sir Keir Starmer promised to reshape the “flabby” state and “unshackle” civil servants from “bureaucracy”.

Disappointing economic growth, higher borrowing costs and lower-than-expected tax revenues have increased the pressure on the government to find savings.

Earlier this week, the government unveiled sweeping changes to the benefits system, including making it harder for people to claim disability payments, with the aim of saving £5bn a year by 2030.

Reeves has signalled she will not raise taxes or government budgets in her Spring Statement next week, telling the BBC this week that “we can’t tax and spend our way to higher living standards and better public services”.

She is constrained by self-imposed rules, including not borrowing to fund day-to-day spending and to see debt fall as a share of the UK economic output by 2029/30.