The chancellor has said she is "confident" 10,000 civil service jobs can be axed after numbers ballooned during the pandemic - as she seeks to cut more than £2bn from the budget.
Rachel Reeves has told Sky News she is certain the government can deliver those cuts to "back office jobs" to free up resources for "front line" services.
She is expected to unveil a raft of spending cuts during the spring statement on Wednesday - and has reportedly ruled out tax rises.
The FDA union has said the government needs to be honest about the move, first reported by The Telegraph, and the "impact it will have on public services".
Reeves concedes cuts won't be pain-free
Appearing on Sky's Sunday Morning With Trevor Phillips programme, the chancellor was pushed repeatedly for a precise number of civil service jobs she wants to cut, and she eventually replied: "I'm confident that we can reduce civil service numbers by 10,000.
"And during COVID, there were big increases in the number of people that were working in the civil service.
"That was the right thing to do to respond to those challenges. But it's not right that we just keep those numbers there forever."
Ms Reeves said there are "a number" of civil service jobs that can be done by technology, while "efficiencies" can also be made by getting rid of quangos.
Asked what roles she expects to no longer need, she said: "It will be up for every department to set out those plans.
"But I would rather have people working on the front line in our schools and our hospitals and our police, rather than back office jobs."
She said cuts will be made to things like travel budgets, spending on consultants, and also on communications.
She conceded that the cuts will not be pain free, but says she would rather spend money to "deliver better public services".
Civil service departments will first have to reduce administrative budgets by 10%, which is expected to save £1.5bn a year by 2028-29.
The following year, the reduction should be 15%, the Cabinet Office will say - a saving of £2.2bn a year.
The chancellor has also said she won't be putting up taxes on Wednesday, telling The Sun On Sunday: "This is not a budget. We're not going to be doing tax raising."
Ms Reeves added: "We did have to put up some taxes on businesses and the wealthiest in the country in the budget [in the autumn].
"We will not be doing that in the spring statement next week."
The chancellor has repeatedly insisted she won't drop her fiscal rules which preclude borrowing to fund day-to-day spending.
Civil service departments will receive instructions from the Chancellor of the Duchy of Lancaster Pat McFadden in the coming week, The Telegraph reported.
"To deliver our Plan for Change we will reshape the state so it is fit for the future. We cannot stick to business as usual," a Cabinet Office source said.
"By cutting administrative costs we can target resources at frontline services - with more teachers in classrooms, extra hospital appointments and police back on the beat."
The move comes after the government last week revealed welfare cuts it believes will save £5bn a year by the end of the decade.
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FDA general secretary Dave Penman said the union welcomed a move away from "crude headcount targets" but that the distinction between the back office and frontline is "artificial".
"Elected governments are free to decide the size of the civil service they want, but cuts of this scale and speed will inevitably have an impact on what the civil service will be able to deliver for ministers and the country…
"The budgets being cut will, for many departments, involve the majority of their staff and the £1.5bn savings mentioned equates to nearly 10% of the salary bill for the entire civil service."
Ministers need to set out what areas of work they are prepared to stop as part of spending plans, he said.
"The idea that cuts of this scale can be delivered by cutting HR and comms teams is for the birds. This plan will require ministers to be honest with the public and their civil servants about the impact this will have on public services."
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Mike Clancy, general secretary of the Prospect union, warned that "a cheaper civil service is not the same as a better civil service".
"Prospect has consistently warned government against adopting arbitrary targets for civil service headcount cuts which are more about saving money than about genuine civil service reform.
"The government say they will not fall into this trap again. But this will require a proper assessment of what the civil service will and won't do in future."
(c) Sky News 2025: Civil service to axe 10,000 jobs, Chancellor Rachel Reeves says - as she eyes cutting £