People should work fewer hours to earn a living, but capping their hours would be unrealistic, a report commissioned by the Labour Party has claimed.
The report, by cross-bench peer Robert Skidelsky, said working less without loss of pay was "good for material and spiritual well-being".
But it said imposing a four-day week - a policy Labour is considering - would not be "realistic or even desirable".
Labour shadow chancellor John McDonnell said he would study the findings.
But the free market Adam Smith Institute warned: "If we force people to work less they will inevitably earn less."
According to the report, working hours in the UK are much lower than during the Industrial Revolution, when people could work up to 16 hours a day.