Boris Johnson and Rishi Sunak have discussed dramatically reducing the number of civil servants further than previously planned to pre-Brexit levels, with one source saying the headcount was around 90,000 lower then, ITV News understands.
They revealed the prime minister and chancellor drew up a plan to start with a recruitment freeze and a new rule banning vacancies being filled without special permission from ministers at a meeting on Monday.
A letter from cabinet secretary, Simon Case, to colleagues - leaked to ITV News - contains more details about the plans- saying the aim is to get to 2016 levels within three years. It confirms that is a cut of 91,000 staff.
It says discussions will start this month and permanent secretaries - the most senior figures in civil service departments - must work with Cabinet ministers to draw up plans.
However, to get anywhere close to 2015/16 levels will raise the prospect of significant job cuts, likely heightening tensions between ministers and civil servants who have already clashed over the question of people working from home.
Unions dismissed the latest discussions as either a "headline-grabbing stunt" or something that would mean government cutting back on delivering key services in areas like health, on borders, or in the passport office.
At the meeting, the prime minister, his chancellor and chief of staff, Steve Barclay, talked about a 25% cut to return Whitehall to its size before numbers were increased to deal with Brexit and then Covid, according to those familiar with discussions.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To know
It isn't the first time the government has raised the prospect of big cuts. Jacob Rees-Mogg, the minister in charge of government efficiency, has previously talked about reducing numbers by 65,000. However, the plan agreed by the prime minister could go significantly further.
According to the Institute for Government the number of staff on full time contracts has risen from 392,500 at the start of 2016 to 475,020 - a rise of around 82,520, or 21%.
Downing Street and Treasury sources are pointing to an even higher target but with no deadline on when to achieve it, some are cynical about the motivation and whether it could be to do with stoking a culture war within Whitehall.
Dave Penman, general secretary of the FDA union, representing senior civil servants, said the expansion in numbers was necessary to deal with the consequences of both the Covid pandemic and Brexit.
"A serious government makes choices," he told ITV News.
"Ultimately they can cut the civil service back to 2016 levels, but they need to decide what the civil service must then stop doing as a consequence. Will the Passport Office be cut back, or the Border Force? Or the Department of Health and Social Care?
"Unless they’ve got a serious plan, it’s either another headline-grabbing stunt or a reckless slash-and-burn to public services without a thought or care about the consequences."
How seriously should we take these signals?
Alex Thomas, programme director at the Institute for Government said that the plan sounded bigger than what had already been announced in the spending review and would make it "impossible to restrict the reductions to 'non-frontline' roles as had been previously announced".
He added: "The civil service has grown a lot since 2016 and some of the most immediate resource demands have passed – so it’s right to look for efficiencies for the taxpayer. There is room to slim down.
"But ministers need to think carefully about the speed and location of the cuts.
"If the government races to reduce headline numbers, institutes blanket recruitment bans and redundancy rounds then the wrong people will leave, some of the wrong people will stay, and the outcome will in the end be worse for the taxpayer."
The plans are being driven by a committee on government efficiency chaired by Sunak.