Prime minister Rishi Sunak warned the UK about a four day working week this year

Rishi Sunak has warned that switching to a four day working week could cost the UK £30 billion.

A number of companies have been working just four days a week instead of five and the vast majority of them have given it a big thumbs up.

Around nine out of 10 companies which tried the four day week found a boost in productivity and an increase in the happiness and health of their workers.

Many companies found they actually made more money with their staff working four days rather than five as the boost in productivity meant they weren't doing less with their time.

The public sector has also give it a go, with South Cambridgeshire District Council starting a four day week trial in January 2023 and deciding in May to extend it by 12 months as it was succeeding.

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However, not everyone reckons it's such a good idea and one of those naysayers is Rishi Sunak, who has just past one year in Downing Street as Prime Minister.

In that time he's not managed to drag the Conservatives back to popularity from the dregs they ended up in during the final disastrous days (not that there were many days) of the Liz Truss era where she was being mocked by a lettuce.

As for his stance on the four day working week, he urged South Cambridgeshire District Council to 'reconsider' when he was told they were extending their trial.

The issue was brought up in the House of Commons in May, with Tory MP Anthony Browne claiming to the Prime Minister that switching to a four day week had led to 'a reduction in services and an increase in costs'.

He also said that think tank TaxPayer's Alliance, which was founded by Vote Leave chief executive Matthew Elliott, had claimed the cost of the public sector switching to four days to be around £30 billion.

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Sunak said it was 'disappointing to hear' that the council was going for a four day working week, so it sounds like the PM is not a fan of this new approach.

Take this with a pinch of salt though, as South Cambridgeshire District Council have said that an independent review of their trial by the University of Cambridge found that in nine of 16 areas measured there was 'substantial improvement' compared to the previous year.

The other seven areas were 'at similar levels' or saw a 'slight decline', while no measurable area of performance dropped to concerning levels.

So whatever Rishi Sunak might think, the vast majority of places giving the four day working week a go are sticking with it.