The Wellcome Trust has scrapped plans to trial a four-day week for its 800 head office staff , saying it would be “too operationally complex to implement”.

The £26bn London-based science research foundation was considering giving workers Fridays off with no reduction in pay. The Wellcome Trust planned to launch a trial this autumn, but on Friday told staff it would not go ahead.

The decision, which followed a three-month study, is a blow to advocates for a four-day week who say it can can improve productivity and wellbeing. The merits of the shorter working week are being examined by Labour, with the shadow chancellor, John McDonnell, asking the political economist Prof Robert Skidelsky to investigate.

Wellcome is the world’s second-biggest research donor after the Bill & Melinda Gates Foundation and would have been the biggest UK employer so far to switch.

But the project foundered when it became clear that work could have become harder for employees in back office and support functions, such as IT, finance and human resources. Other parts of the business where tasks were easier to handle with flexibility might have benefited from the switch but it was felt it was unfair to proceed.

There was also concern that compressing work into a Monday to Thursday window could negatively affect the wellbeing of some workers, reducing productivity. Since January Wellcome has been asking teams to consider how they would adapt to a four-day week. So many contrasting ways emerged that senior management concluded they would not all fit together without causing significant disruption and threatening operations.

“After extensive internal consultation on whether we should trial the four-day week, we have concluded that it is too operationally complex to implement,” said Ed Whiting, the director of policy and chief of staff. “We have learned a lot through our consultation process and, although we will not be trialling a four-day week, we remain committed to maximising the impact Wellcome can make in the world through supporting the wellbeing and productivity of our staff.”

In January, Whiting, a former adviser to David Cameron, said Wellcome hoped a four day-week could deliver “a healthier workforce, a reduction in sickness absence and improved sense of work-life balance”.

The proposed move came amid a growing interest in a compressed working week. Pursuit Marketing, a marketing company in Glasgow that switched 120 people to four days in late 2016, has said it has been instrumental in a 30% increase in productivity. Perpetual Guardian, a New Zealand trust business that supervises almost NZ$200bn (£103bn) in assets, reported a 20% increase after switching its 240 employees. But a University of Auckland study found increased stress among some people because of shorter timeframe to complete tasks.

The experience of Wellcome may suggest that organisations with workers carrying out a wide range of functions – it employs exhibition curators as well as fund managers – could find it harder to switch their entire business to the shorter week.

Many of those making the move tend to be smaller. In the last six months, they have included: Synergy Vision, a medical communications agency with 45 employees; Elektra Lighting, a lighting design company; Lara Intimates, which makes underwear; and the Intrepid Camera company, which makes and exports photographic equipment.

There has been opposition to the four-day week from the CBI. The business organisation has said that “rigid approaches feel like a step in the wrong direction” at a time when flexible working is seen as increasingly essential.

But the TUC last year called for a wholesale reduction of working hours in the UK, citing research that found almost half of workers want a four-day week. It said UK workers put in the longest hours in the EU, behind only Austria and Greece.



