Hundreds of British workers will be given greater choice over their hours as part of a new pilot by the official four-day week campaign.

The six-month project will build on the original 2022 trial, with employers also trying flexible start and finish times, a nine-day fortnight, and compressed hours.

Six businesses have already signed up and the campaign’s director told the BBC it is hoping to target around 3,000 employees and 50 companies.

The UK’s biggest union Unison and several big firms support the experiment, but other companies have abandoned the four-day week after trying it.

The campaign’s director Joe Ryle said “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 campaign is backed by research from Cambridge University and Boston College, with Welsh community housing landlord Bron Afon Community Housing one of the first companies to sign up to the latest trial.

Director Unji Mathur said she has already been “impressed” by the impact a shorter working week has had on organisations’ performance, as well as employees’ wellbeing and retention.

She added that she sees the trial as a chance to help improve employees’ work-life balance.

The campaign group said that “at least” 54 of the 61 companies that took part have maintained the four-day week a year and a half after the original trial.

Sophie Greaves works with flexible start and end times at her research chemist role in Liverpool.

She can clock in anytime between 07:00 and 10:00 Monday to Friday and leave when her shift finishes eight hours later.

She believes the flexibility is good for days when you want to start later, or if you wake up early and are “twiddling your thumbs” at home.

“People really are productive if they can manage their own time,” she says.

Asda, however, shelved a four-day week trial last week after staff complained that their longer shifts were too demanding.

Under its plans, store managers worked 45 hours across four days. Other parts of the trial, which included working 39 hours across five days, were more popular.

Morrisons also abandoned the four-day week for staff at its corporate office in Bradford in January.

Staff were required to work 37.5 hours across four days with occasional Saturday shifts.

Responding to Morrisons’ decision, Mr Ryle said this was “not really a four-day week”, which he defines as 32 hours across four days.

Meanwhile, some companies are trying another direction. Earlier this month, Greece introduced a six-day working week for certain industries in a bid to boost productivity and economic growth in turn.

It only applies to businesses which operate 24-hours a day and is optional for workers, who get paid an extra 40% for the overtime they do.

Mr Ryle will present the results of this second trial to the newly-elected Labour government next year.

“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,” he said.