The biggest civil service union has warned of strike action over Boris Johnson’s “P&O-style” approach to cutting 91,000 Whitehall jobs, with ministers also seeking to reduce staff redundancy terms by up to a third. The plan to cut one in five civil service jobs caused alarm and dismay across government departments, after Johnson told his cabinet to spend the next month finding ways to cut the civil service back to pre-Brexit levels within three years. He claimed it was necessary to shrink the size of central government to tackle the cost of living crisis. The combative move by Johnson, briefed to the Daily Mail, comes on top of existing civil service anger over pay increases less than half of the current 7% rate of inflation, the Cabinet Office drive to get them back into the office and overwork from Covid backlogs. At the same time, ministers have told trade unions they are also trying to return to previously defeated plans to cut redundancy packages in the civil service by up to 33%. In a further shake-up, Steve Barclay, the Cabinet Office minister and No 10 chief of staff, said all senior civil service jobs would in future have to be advertised externally as well as internally. While taking on the civil service, Johnson made a fresh call to get employees in the public and private sector back to the office after the pandemic. The government had previously said it was up to businesses to figure out where their workforces should be based. But in an interview with the Daily Mail, he said: “We need to get back into the habit of getting into the office. I believe people are more productive, more energetic, more full of ideas, when they are surrounded by other people. “My experience of working from home is you spend an awful lot of time making another cup of coffee, and then you know, getting up, walking very slowly to the fridge, hacking off a small piece of cheese, then walking very slowly back to your laptop and then forgetting what it was you’re doing.” Mark Serwotka, the general secretary of the Public and Commercial Services (PCS) union, representing about 180,000 public sector workers, warned that the civil service had reached the “tipping point” of national strike action being realistic. “We have our conference in 10 days’ time where I’m as certain as I can be that we will move to a national strike ballot, probably in September,” he said. He said the civil service was already struggling with backlogs of passports, driving licences, court cases, and pension payments due to “chronic understaffing and a recruitment crisis”. “Six weeks ago we were all outraged about P&O and now half a million civil servants have woken up to the media saying one in five jobs must go,” he added, referring to P&O Ferries’ recent sacking of nearly 800 crew. Dave Penman, the general secretary of the FDA union, which represents 19,000 senior civil servants, said it had been like a “kind of P&O: civil servants finding out about one in five jobs having to go via the Daily Mail” and that the 91,000 number had been “plucked out of thin air”. Kevin Brandstatter, a national officer at the GMB union, which represents a large number of Ministry of Justice staff, said: “This is a complete bombshell for the civil service and it’s not clear yet where the axe will fall. But if the cuts hit GMB members in the Ministry of Justice it will have a massive impact on legal aid and everyone’s right to proper representation.” Permanent secretaries wrote to their departments on Friday, with some expressing regret at the way the news of cuts had been conveyed. Jim Harra, the permanent secretary at HM Revenue and Customs, sent a message to staff saying: “I am sorry that you have learned this from the media rather than from me or civil service leaders.” Defending the plans, the minister for Brexit opportunities, Jacob Rees-Mogg, said it was not a return to austerity because pre-Brexit vote levels were “reasonable”. Downing Street also did not rule out compulsory redundancies, though No 10 said it was hoped many of the cuts would come through “natural wastage”. Experts also questioned the prime minister’s claim the cuts would help with the cost of living. Richard Murphy, professor of accounting at Sheffield University, said: “Cutting employment does not cut the cost of living. It just makes the cost of living crisis very much worse for some, and for the rest of us it deprives us of the benefit of their spending – meaning we’re worse off too.” Johnson’s plan was also challenged by Margaret Hodge, the Labour MP and former public accounts committee chair, who said it was a “telling sign of a government flat out of ideas”. “While the cost of living crisis rages on, you can put their plans for real reform on a cigarette paper. Our hollowed-out civil service is in dire need of more expertise, not less,” she said. Tony Wilson, the director of the Institute for Employment Studies, said ministers should reduce the number of civil service jobs created to cope with the pandemic, but the scale of the cuts was “fanciful and damaging to the ability of the civil service to develop policy”. He added: “If the government wants to deny the Ministry of Defence some of the 50,000 civilians who support the work of the armed forces, cut the number of tax collectors employed by HMRC, reduce the Home Office’s Border Force and hit the courts system with yet more cuts, it should go ahead. “The cuts would also damage the DWP’s ability to find people made redundant new jobs, including civil servants put out of work by the new plan.” Jonathan Portes, an economist at King’s College London, said: “The cheapest and least painful way to reduce numbers is a hiring freeze – but that is also a recipe for inefficiency and poor resource allocation … often meaning higher consultancy bills. Redundancies, on the other hand, cost money and reduce morale.”