In the largest public sector trial of the four-day week in Britain, fewer refuse collectors quit and there were faster planning decisions, more rapid benefits processing and quicker call answering, independent research has found.

South Cambridgeshire district council’s controversial experiment with a shorter working week resulted in improvements in performance in 11 out of 24 areas, little or no change in 11 areas and worsening of performance in two areas, according to analysis of productivity before and during the 15-month trial by academics at the universities of Cambridge and Salford.

The trial by the Liberal Democrat-controlled authority drew a furious reaction from the Conservative government, with a minister telling the borough leader, Bridget Smith, to “end your experiment immediately”, complaining that it would not give value for money for local taxpayers.

The Tory former local MP, Anthony Browne, who was defeated by a Liberal Democrat in last week’s general election, had attacked the trial as “an ideological crusade”.

The multi-year study of the trial involving about 450 desk staff plus refuse collectors found:

• Staff turnover fell by 39%, helping save £371,500 in a year, mostly on agency staff costs.

• Regular household planning applications were decided about a week and a half earlier.

• Approximately 15% more major planning application decisions were completed within the correct timescale, compared with before.

• The time taken to process changes to housing benefit and council tax benefit claims fell.

On the downside, rent collection for council housing worsened slightly, although this was attributed to the cost of living crisis. The speed with which empty council houses were relet fell slightly, from 28 to 30 days on average. The results were adjusted for the impact of the Covid-19 pandemic.

Joe Ryle, the director of the 4 Day Week Campaign said the results heralded “a huge opportunity for councils and organisations across the public sector to start planning for a four-day working week”.

The new Labour government is expected to push the NHS to work longer hours to reduce waiting lists, with more operations at weekends, and is preparing to speed up the planning process to boost housebuilding.

Productivity has flatlined in the British economy since the pandemic after historically rising at about 2% annually. In 2019, Labour under Jeremy Corbyn included plans to cut the working week to 32 hours with no loss of pay in its manifesto, but this year the party said nothing about enabling a four-day week in its latest promises. It has pledged to deliver economic growth and productivity growth across the economy to enable greater spending on public services without raising income tax, national insurance and VAT.

Employers everywhere from Sweden to the United Arab Emirates and New Zealand to the US have experimented with the four-day week. But last week the government of Greece announced a new six-day week policy for private companies aimed at boosting the economy amid a shrinking population and shortage of skilled workers. It is seeking longer hours from workers to turbocharge productivity.

Under the South Cambridgeshire trial, which began in January 2023 and ran to April 2024, staff were expected to carry out 100% of their work in 80% of the time for 100% of the pay. The full trial cut staff turnover by 39% and scores for employees’ physical and mental health, motivation and commitment all improved, the study showed.

“Coupled with the hundreds of thousands of pounds of taxpayer money that we have saved, improved recruitment and retention and positives around health and wellbeing, this brave and pioneering trial has clearly been a success,” said John Williams, the lead council member for resources. “We know we cannot compete on salary alone and have needed to find bold new ways of tackling our recruitment and retention issues.”

Mike Davey, the leader of Cambridge city council, which shares planning services with South Cambridgeshire, described the trial as “a win-win-win situation, with improved service delivery for residents, reduced staffing costs for the council, and a better work-life balance for council staff.”

Scores of private companies have already adopted the approach, with many finding it helps staff retention. Ryle said the South Cambridgeshire results “prove once and for all that a four-day week with no loss of pay absolutely can succeed in a local government setting”.