A second pilot of a four-day week is scheduled to launch this autumn as campaigners urge employers to sign up.
The organisers are hoping the Labour government will be more receptive to the project than the former Conservative administration.
The four-day-week pilot has opened for companies to sign up for a November start, with findings to be presented to the government in the summer of 2025.
It will be run by the UK’s 4 Day Week Campaign and Timewise, the flexible working consultancy, with training for employers starting in September. Researchers at the University of Cambridge, Boston College and the Autonomy Institute will support the analysis.
More than 60 companies took part in the first UK four-day week pilot in 2022, with 54 keeping their new working arrangements 18 months later.
“With a new Labour government, change is in the air and we hope to see employers embracing this change by signing up to our pilot,” said Joe Ryle, director of the 4 Day Week Campaign.
The Conservatives did not welcome the policy, with ministers clashing with Liberal Democrat-run South Cambridgeshire District Council over its 15-month trial.
Last summer, the then local government minister Lee Rowley wrote the local authority asking it to “stop your experiment immediately”.
This week, the South Cambs four-day week trial showed improvements in performance in 11 out of 24 areas, little or no change in 11 areas, and a worsening of performance in two areas, according to the analysis by the universities of Cambridge and Salford. It found that fewer refuse collectors resigned from their jobs and that planning decisions were made and calls were answered faster.
The latest pilot will also assess other flexible working arrangements, including a shorter working week, flexible start and finish times, a nine-day fortnight and compressed hours.
Under Jeremy Corbyn’s 2019 manifesto, a four-day arrangement appeared as a 10-year pledge to reduce average full-time weekly working hours to 32 across the economy, but Keir Starmer’s manifesto this year did not include such a commitment.
Nevertheless, many cabinet ministers are supportive of the idea, together with some trade unions.
Ryle added: “As hundreds of British companies and one local council have already shown, a four-day week with no loss of pay can be a win-win for workers and employers.
“The nine-to-five, five-day working week was invented 100 years ago and is no longer fit for purpose. We are long overdue an update.”
Claire Campbell, chief executive of Timewise, told the Guardian that it wanted to see more “site-based, shift-based workers sign up because this is where innovation is needed most”, adding that a four-day week “will benefit worker health and retention”.
Sign up to our weekly round-up of HR news and guidance
Receive the Personnel Today Direct e-newsletter every Wednesday