Civil servants were advised that a four-day workweek is the last thing the UK economy needs.
The 4 Day Week Campaign has more than 150 approved companies, and it is claimed to have positive effects on employee retention and stress reduction.
The Department of Environment, Food, and Rural Affairs civil servants have filed a petition for a four-day trial week.
Critics countered that reducing working hours by a fifth would just exacerbate the productivity challenges currently plaguing public sector firms.
Former Cabinet minister Sir Jacob Rees-Mogg declared: “After 30 years of low productivity growth the last thing the UK economy needs is a shorter working week. This is especially true of the public sector which is less productive now than it was in 1997.”
The Public and Commercial Services union (PCS) said its proposal would involve a 20% reduction in working hours for staff with no loss of wages.
The move followed pressure from some government ministers to increase the amount of time civil servants spend in their workplaces.
Former Cabinet Minister Sir John Redwood added: “It should be left to employers and employees.
“If you have got a highly productive workforce then that is something you could negotiate with them on.
“But if you have got a productivity problem, you would need to get productivity sorted before you even start to think about it.
“You can’t afford a big drop in productivity with a loss of a fifth of the working time.
“It has got to be affordable. This decade, productivity has fallen 7%.
“That’s why we are running out of money.”
Joe Ryle, director of the 4 Day Week Campaign, claimed official figures showed that almost two million workers reported suffering from work-related ill health in 2022/23.
This, he said, demonstrated the urgency of a cut in the working week.
He said: “Our very British culture of long working hours and low pay is pushing people to the brink.
“We work some of the longest hours in Europe which is causing burnout for millions and not producing good results for the economy.
“We are long overdue a reduction in working hours. The time has come for a four-day working week, with no loss in pay.”