A Reform UK plan to cut the size of the civil service would involve sacking more planning officers than exist and getting rid of at least two-thirds of the psychologists who support prison officers’ welfare, it has emerged.

The policy paper, led by the Reform MP Danny Kruger and published in December, promises to save more than £5bn a year by cutting civil service roles, with the full-time-equivalent (FTE) headcount falling by 13%.

Titled Storm and Sunshine, the report calls for a particular focus on areas such as communications, where it says numbers would be reduced by 60%, and human resources, where a two-thirds reduction is envisaged.

Among detailed proposals for other areas, the paper calls for a “reduction of 450 FTEs in planning, accounting for £40m a year”. According to the 2025 statistics for civil servants employed in each role, however, there are only 445 planners employed across the civil service in Britain, about a third of them at the Ministry for Housing, Communities and Local Government (MHCLG).

Asked how it would be possible to sack more planners than existed, a Reform spokesperson said the total included 440 people employed as planning inspectors at the MHCLG. “Our number stands,” they said.

The inspectors work for the Planning Inspectorate, an arm of the MHCLG which decides on planning appeals and deals with recommendations for major infrastructure projects such as power plants. It is not clear how well this work could continue after significant staff cuts.

Another part of the Reform plan pledges to cut 930 occupational psychology roles, saving £60m a year. The civil service statistics show that of 1,390 psychologists, 90% work in the prison and probation service, where they primarily help prison staff.

Asked about the potential consequences for the welfare of prison staff if the cut were to happen, a Reform spokesperson said: “Prisons will be much safer places to work under a Reform government and working conditions for prison officers will be greatly improved.”

Another measure, which according to the report would save £150m a year, would be to cut 2,500 security roles, or about a quarter of the total across the civil service.

The bulk of them, about 7,000, are either in the Ministry of Defence, often guarding bases or other sensitive sites, or in the Foreign Office, which includes cybersecurity roles. A Reform spokesperson said the party had not said which departments would be targeted.

The shadow Cabinet Office minister, Mike Wood, said: “This is yet another of Reform’s policies that isn’t worth the paper it is written on.

“Not only does their plan propose cuts to teams larger than the number of people employed in them, it would also slash security staff who protect sensitive sites and cybersystems, while gutting psychological support in our prisons.

“They are not a serious party. No doubt it will only be a matter of time before they are publicly fighting over this policy too.”