Imagine there was a single policy that would slash unemployment and underemployment, tackle health conditions ranging from mental distress to high blood pressure, increase productivity, help the environment, improve family lives, encourage men to do more household tasks, and make people happier. It sounds fantastical, but it exists, and it’s overdue: the introduction of a four-day week.

The liberation of workers from excessive work was one of the pioneering demands of the labour movement. From the ashes of the civil war, American trade unionism rallied behind an eight-hour day, “a movement which ran with express speed from the Atlantic to the Pacific, from New England to California”, as Karl Marx put it. In 1890 hundreds of thousands thronged into Hyde Park in a historic protest for the same demand. It is a cause that urgently needs reclaiming.

Many Britons work too much. It’s not just the 37.5 hours a week clocked up on average by full-time workers; it’s the unpaid overtime too. According to the TUC, workers put in 2.1bn unpaid hours last year – that’s an astonishing £33.6bn of free labour.

That overwork causes significant damage. Last year, 12.5m work days were lost because of work-related stress, depression or anxiety. The biggest single cause by a long way – in some 44% of cases – was workload. Stress can heighten the risk of all manner of health problems, from high blood pressure to strokes. Research even suggests that working long hours increases the risk of excessive drinking. And then there’s the economic cost: over £5bn a year, according to the Health and Safety Executive. No wonder the public health expert John Ashton is among those suggesting a four-day week could improve the nation’s health.

So the renewed call for a four-day week from Autonomy Institute is very welcome. “We want to shift people’s perspectives, to better work and less work,” says the thinktank’s Will Stronge. Indeed, a deeply unhealthy distribution of work scars our society. While some are working too much, with damaging consequences for their health and family lives, there are 3.3 million or so “underemployed” workers who want more hours. A four-day week would force a redistribution of these hours, to the benefit of everyone. This will be even more important if automation in sectors such as manufacturing, administration and retail creates more poorly paid work and more underemployment.

A four-day working week could also help tackle climate change: as the New Economics Foundation thinktank notes, countries with shorter working weeks are more likely to have a smaller carbon footprint. This is no economy-wrecking suggestion either. German and Dutch employees work less than we do but their economies are stronger than ours. It could boost productivity: the evidence suggests if you work fewer hours, you are more productive, hour for hour – and less stress means less time off work. Indeed, a recent experiment with a six-hour working day at a Swedish nursing home produced promising results: higher productivity and fewer sick days. If those productivity gains are passed on to staff, working fewer hours doesn’t necessarily entail a pay cut.

Then there’s the argument for gender equality. Despite the strides made by the women’s movement, women still do 60% more unpaid household work on average than men. An extra day off work is not going to inevitably lead to men pulling their weight more at home. But, as Autonomy suggests, a four-day week could be unveiled as part of a drive to promote equal relationships between men and women. A national campaign could encourage men to use their new free time to equally balance household labour, which remains defined by sexist attitudes.

It is heartening to see the resurrection of one of the great early causes of the labour movement. Germany’s biggest union, IG Metall, is calling for a 28-hour week for shift workers and those with caring responsibilities.

That said, on its own the demand is not enough. Now that socialism is re-emerging as a political force that can no longer be ignored or ridiculed, the struggle for more time for leisure, family and relaxation should be linked to broader fights. Increased public ownership of the economy should be structured to create more worker self-management and control. If technology means a further reduction in secure work, a universal basic income – a basic stipend paid to all citizens as a right – may become ever more salient.

Sure, work can be a fulfilling activity for some. It strikes me, though, that few would disagree with the notion that we should spend more time with our families, watching our children grow, exercising, reading books, or just relaxing. So much of our lives is surrendered to subordinating ourselves to the needs and whims of others, turning human beings into cash cows rather than independent, well-rounded individuals.

Our social model means economic growth all too often involves concentrating wealth produced by the many into the bank accounts of the few, without improving the lives of the majority. Growth should deliver not just shared prosperity and improved public services but a better balance between work, family and leisure.

Labour politicians now position themselves as the harbingers of a new society, not mere tinkerers with the existing order. That must surely mean building a new economy that lightens the freedom-sapping burden of work. Labour may win the opportunity to build a socialist Britain. If it does, it must be ambitious enough to liberate citizens from the excesses of work.