These companies employ more than 5,000 people (charities, marketing and technology businesses are best represented) with proponents saying that it provides a better work/life balance, better attraction and retention of staff and improved productivity.
The largest proportion of these companies are in London (59 of the total) and are largely in marketing, advertising and PR (30 companies in total).
Joe Ryle, 4 Day Week Foundation’s campaign director, said that the extra day "gives people the freedom to live happier, more fulfilling lives".
Read more: Four-day week continued by most trial participants
But getting there is no small task. A four-day week trial started at South Cambridgeshire District Council in 2023 has attracted political criticism about how roles are performed, and what workers do with time off.
This is despite a 2022 thinktank report from Autonomy, the University of Cambridge and Boston College finding that cutting a day off the working week resulted in staff suffering less stress, burnout and fatigue.
The same report revealed that 15% of employees said that no amount of money would induce them to accept a five-day schedule over a four-day week.
Gary Cookson, who works a four-day week as founder of the consultancy EpicHR, said that getting past reticence to a four-day week might include overcoming the 'we have always worked this way' mindset of various stakeholders as well as understanding customer and branding fears.
He told HR magazine: “Just because employees work one less day per week, no one said that the organisation had to close on that day – why would it?
“Customers increasingly use organisations at times when the majority of that organisation’s employees are not working – and those organisations use different working and shift patterns to cope.”
In addition, with some firms worried about how to do this, Cookson adds that during the height of the Covid-19 pandemic many firms showed that they could move away from traditional models of working.
He added: “Hybrid working has already shifted measurement of work away from input and hours worked and more towards outputs and outcomes.
“For some organisations, the change to the working week is a natural consequence of making the change to more effective remote and hybrid working.”
Cookson said that some staff might also be worried that the shorter working week could impact pay, burnout and the ability to complete workplace tasks.
Read more: Less than 2% of job ads offer four-day weeks
These worries should be addressed from the get-go if the firm is thinking about evolving the working week, said Felecia Wood, director of client experience and consultancy at HR consultancy Croner.
Speaking to HR magazine, she said: “Businesses can choose to combat any backlash received by communicating the rationale and benefits of their decision [to employees] but also to clients, to reassure clients that service will not be impacted.”
Wood added that businesses should review roles, approaches to deadlines and service coverage periods, how different jobs exist within a four-day structure, and, critically, what the business wants to achieve with the move.
She said: “Has the move been prompted by a need to retain or recruit talent, or a need to better employee wellbeing? If so, will the move achieve this? Or is the aim to reduce costs?
“Dependent on the aim, the way any four-day working week is implemented may change.”
In addition, with employees able to ask for flexible working, businesses may want to consider how this impacts their own employee management and business plans, Wood continued.
She added: “All employees have the right to request flexible working, which could include asking their employer to work a four-day week, or in reverse asking to work a five-day week if an employer has chosen to implement the former.”