I meet Rich Leigh for a coffee in Gloucester on a Friday, his day off. In fact, his entire company has the day off, because Radioactive PR, the firm led by Leigh, 30, has adopted a four-day week.

It is one of a handful of UK businesses that now operate like this: staff still get paid their previous five-day salary, but they work a day less. The company began with a six-week trial and found that they achieved just as much – and there were even signs of growth. The key to the scheme’s success, Leigh says, is how happy his employees now are. “There are two ways to make money in my line of work,” he says, “retain clients and get new ones. Miserable, tired staff can’t do either.”

The four-day working week is being touted by some as the answer to Britain’s “productivity problem”. British people work some of the longest hours in Europe: the average British worker takes only a 34-minute lunch break and works 10 hours overtime each week (more often than not, this is unpaid). Yet UK productivity lags seriously behind our European neighbours, who tend to work fewer hours. France recently made it illegal to expect workers to answer emails out of hours, and the average French worker produces more by the end of Thursday than their UK counterparts do in a full week.

British working practices have taken their toll on the nation’s health and happiness. More than half a million workers in the UK were signed off with work-related stress or anxiety last year. That amounts to 12.5m working days, and while it is difficult to quantify the financial cost of this, a 2014 study put it at nearly 4.5% of GDP. Moreover, the work landscape itself is changing. Automation and AI will have a significant impact on the labour market, while insecure work becomes more commonplace.

The EU working time directive sets a limit of 48 working hours a week. Britain is the only EU member that allows workers to opt out of this and work longer hours, a practice that trade unions have argued has been subject to “widespread abuse”.

For campaigners, now is the time for a change. There is both opportunity and need, on health, happiness and business grounds. Those who have called for the introduction of a four-day week include the Green party and Frances O’Grady, the general secretary of the Trades Union Congress. O’Grady argues that where businesses have increased their profits as a result of automation, that success should be shared with workers in the form of reduced hours: “It’s time to share the wealth from new technology, not allow those at the top to grab it for themselves,” she says.

At Radioactive, Leigh says the switch to the four-day working week was surprisingly straightforward, although there have been some sacrifices: lunchtimes have been reduced to 45 minutes and annual leave by 20%.

Angharad Planells says a four-day week has made her less stressed about going back to work after maternity leave. Photograph: Adrian Sherratt/The Guardian

For Angharad Planells, who works at Radioactive, the change has made it easier for her to prepare for the birth of her first child. “You can argue that with four days you have less time to do all the work, but we’ve had new hires to help [keep stress down]. Anyway, as long as you get the results, what does it matter?”

It is thought that a four-day working week would have a particularly big impact on women, given the caring responsibilities and unpaid domestic labour they often end up undertaking. At the very least, it would be one less day of childcare for families to pay for. “It’s made me feel less stressed about coming back after maternity leave,” says Planells. Could she ever go back to a five-day week? “Honestly, I don’t see myself ever leaving,” she says. “Did I mention how many CVs we’ve had in since people found out we went four days?”

The four-day week doesn’t mean working 40 hours over four days, nor is it about shift patterns. Rather it is about working a 28- to 32-hour week but being paid for a 35- to 40-hour, traditional full-time job. In Edinburgh, workers at the tech firm Administrate are also four days a week, although the office is open five – some people work Monday to Thursday others Tuesday to Friday.

Administrate introduced the four-day week in 2015. “It was an experiment,” says John Peebles, the CEO. “We wanted to see: if we invest in our people, will the financial outcome be better than if we pinched every penny?”

Efficiency has made up for the loss of working hours. “In a lot of tech companies, time is lost to overly long meetings,” says Peebles, “or having beers in the last hour. But what if we just worked really hard for 32 hours a week and didn’t have any downtime?” Administrate has rules on keeping meetings short and encourages team bonding to take place in set spaces (regular team lunches, for example).

Overwhelmingly, the scientific evidence has said that working shorter hours makes us more productive. But the idea of the four-day working week hasn’t convinced everyone. Mark Price is a former managing director of Waitrose and a former deputy chairman of the John Lewis Partnership; he also served as trade and investment minister under David Cameron. Price can’t see the four-day week taking off in the public sector, where many jobs involve shift patterns that cover 24 hours a day, seven days a week. “If everybody in the public sector was to work 28 hours a week rather than 35,” he says, “you would have to increase the pay bill by 20% to cover that. It would mean taxes going up. I can’t imagine there is much of an appetite for that.”

Price is also concerned by the sentiment behind the movement, which he says is, in part, “the assumption that work isn’t good, so you should do less of it”. He points to the phrase “work-life balance”, which “implies that life is not work”, and argues that rather than concentrating on the quantity of work we do, we should focus on the quality.

“We should be thinking about workplace happiness and engagement,” he says. “I know there is a lot of awfully dull and repetitive work that would be great for computers to take away. But then there’s other work that is stimulating, and the question is how we create those jobs into the future.”

At the heart of this discussion are some very complex questions: what is work? Is there a difference between good work and bad work, and why is some work paid well and other work less so? Commutes in the UK are getting longer as housing prices in city centres rise, and it is becoming increasingly common for people to answer their emails while commuting. Should that count towards our overall tally of hours?

Aidan Harper is the founder of the 4 Day Week campaign. He wants to ensure that a shorter working week is universally guaranteed for all workers, either by legislation or trade union bargaining.

“In the UK, we have growing numbers of overworked people,” says Harper, “but we also have a growing number of underworked people, namely gig economy employees looking for more work. So one question is whether the redistribution of time, of workload, might help this.

“And there is a more potent question about what the economy is for. Surely the purpose of the economy is to create a good life within it, and have a material basis from which you can be housed, have an education etc. But something our economy is not providing for us is time, which we need. The next stage in economic development should not be to generate more stuff, but to create the conditions in which we can live good lives.”

Harper points to the role campaigners and everyday workers have in pushing for positive change. The five-day working week was itself the result of negotiations by unions in the early 20th century – observing technological advances in factories, they negotiated for a formal weekend rather than just a single Sunday off.

For Peebles, the time is right to reassess. “Business is different today than 30 years ago, when I couldn’t send an email, couldn’t shop online, had to use a fax machine. So why are we working the same way?”

In Gloucester, Leigh is keen to beat the commuter traffic and enjoy the rest of his day off. “Most businesses in the UK are like mine, fairly small,” he says, “one to 10 employees and working in the service industry. So all I’m saying is: why not try it?”