Sir Keir Starmer faces a clash with Civil Service unions after vowing to reshape the “flabby” state and slash the cost of bureaucracy.

The Prime Minister said the Civil Service had grown by 130,000 since the Brexit referendum but services had not improved and it was “overstretched, unfocussed and unable to deliver the security people need”.

But union leaders accused Sir Keir of “using the language of blame” to attack officials and called on him to avoid the “incendiary rhetoric” of Elon Musk’s Department of Government Efficiency (Doge) in the US.

As well as vowing to cut the cost of regulation by 25%, Sir Keir will use a speech on Thursday to promise to refocus the state on his key missions and create “an active government that takes care of the big questions, so people can get on with their lives”.

He will take aim at a “cottage industry of checkers and blockers slowing down delivery for working people”, stepping up his criticism of regulation in the UK.

Sir Keir will announce plans for greater use of artificial intelligence (AI) and technology across the Civil Service, promising that one in 10 officials will work in tech and digital roles within the next five years.

Before the speech setting out his plans, Sir Keir wrote in the Daily Telegraph: “In such uncertain times, people want a state that will take care of the big questions, not a bigger state that asks more from them. We need to be operating at maximum efficiency and strength.

“I believe in the power of the state. I’m not interested in ideological arguments about whether it should be bigger or smaller. I simply want it to work.”

At the moment businesses are having to deal with “an overcautious flabby state” that gets in the way, he added.

Reducing the size of the Civil Service and increasing the proportion of officials working in digital and data roles could save taxpayers up to £45 billion, the Government believes.

Dave Penman, general secretary of the FDA union representing senior officials, said “many civil servants will be looking for the substance and feeling that, once again, the Prime Minister is using the language of blame rather than transformation”.

He added: “Regulators are set up by ministers to regulate – if there’s a cottage industry at large then it’s because that’s what previous governments have wanted.

“Blaming public servants for doing the job they were tasked with by ministers is just cheap politics and is increasingly following a pattern where the Government appears more interested in headlines than leadership.”

Mike Clancy, general secretary of the Prospect union, said it was “right that the Government are pressing ahead with plans to make better use of new tech”, but added it would “find it challenging to compete for the skills needed” without increasing pay.

He added: “Civil servants are not hostile to reforms but these must be undertaken in partnership with staff and unions.

“I urge everyone in Government to avoid the incendiary rhetoric and tactics we are seeing in the United States, and to be clear that reforms are about enhancing and not undermining the Civil Service.”

Technology Secretary Peter Kyle denied that the Government’s plans to reform the civil service were comparable to the Donald Trump administration’s Doge.

He told LBC: “This is a disruptive programme. But it is a programme that will positively disrupt and we want to lead people through it.

“We don’t want to scare people with the prospect of change, we want to excite people with the prospect of change.”

Shadow chancellor of the Duchy of Lancaster Alex Burghart said: “Labour is not serious about getting Britain growing.

“The Prime Minister has no plan to reform the Civil Service or cut public spending.

“Thanks to his budget the size of the state will reach a staggering 44% of GDP by 2030.”

Liberal Democrats leader Sir Ed Davey dismissed Sir Keir’s proposals as “tinkering around the edges while our economy continues to stutter”, and called for an “ambitious new deal with the EU” to boost trade and grow the economy.