Many UK firms taking part in a four-day working week trial have said they will keep it in place after the pilot ends.

More than 70 firms are taking part in the scheme where employees get 100% pay for 80% of their normal hours worked.

At the halfway point in a six-month trial, data shows that productivity has been maintained or improved at the majority of firms.

Though some "old-fashioned" companies taking part in the trial had found the shift to a four-day week "trickier".

Joe O'Connor, chief executive of 4 Week Global, which is running the scheme across a number of countries, said: "We are learning that for many it is a fairly smooth transition and for some there are some understandable hurdles - especially among those which have comparatively fixed or inflexible practices, systems, or cultures which date back well into the last century."

The trial is being run by 4 Day Week, a group campaigning for a shorter working week, along with Autonomy, a think tank and researchers at Cambridge and Oxford universities.

Of the 73 companies in the trial, 41 firms responded to a survey midway through the scheme. Around 86% of those surveyed said they would keep the four-day week policy going after the trial ends.

The majority of firms said it is working well for their business, while 95% said productivity had stayed the same or improved during the shorter week.

More than 3,300 employees are getting one paid day off per week through the course of the trial.

4 Day Week said that employees had benefitted from lower commuting and childcare costs and claimed that a parent with two children would save £3,232.40 on average per year or roughly £269.36 per month.

Will Stronge, director of research at Autonomy, said: "A four-day week with no loss of pay could play a crucial role in supporting workers to make ends meet over the next few years."

Waterwise, which campaigns to decrease how much water is used in the UK, is one of the firms taking part in the scheme and says its team are now "pretty happy" - but it took some getting used to.

"It wasn't a walk in the park at the start." said Waterwise managing director Nicci Russell. "But no major change ever is.

"We have all had to work at it," she said. "Some weeks are easier than others and things like annual leave can make it harder to fit everything in, but we're much more settled with it now overall than we were at the start."

"We certainly all love the extra day out of the office and do come back refreshed. It's been great for our wellbeing and we're definitely more productive already."

The UK trial is part of pilots happening in the US, Ireland, Australia and New Zealand.