Chancellor’s £25bn tax raid on workers and businesses public sector workers also largely exempt, with figures released by the budget watchdog showing the public sector pay bill will rise much faster than private sector wages for the rest of the decade.

In total, the number of state employees is expected to exceed 6 million for the first time.

Public service productivity – a measure of output per hour worked – remains lower than it was in 1997 and 8.5% below pre-pandemic levels at the end of 2019, after a slump during the Covid lockdowns from which it has not recovered never.

The ONS said it had revised down forecast public sector productivity growth from 2.6% to 1% in 2022, adding that this suggested “the recovery of public service productivity from the pandemic is taking longer than previously estimated”.

By comparison, total productivity, measured by hourly output across the economy, was 2% above pre-Covid-19 levels in the three months to September as the private sector noted its weakness.

The Office for Budget Responsibility (OBR) has estimated that private sector workers will be hundreds of pounds worse off by the end of next year because of Ms Reeves’ changes to National Insurance, as employers will foot the bill with smaller pay rises.

Public sector employees, who already enjoy benefits such as gold-plated pensions, will not be largely affected.

Douglas McWilliams, co-chair of the Growth Commission, blamed “bad management” for the poor performance.

Mr McWilliams, who was a government adviser, said: “People (in the public sector) are not being promoted entirely on the basis of management ability, there is too much emphasis on non-performance factors such as diversity, inclusion, gender and things like that.

“On top of that, there seem to be people in the public sector who don’t think productivity is one of their goals.”