Workers could be given the right to ask their employers to work a four-day week under government plans to increase flexible working.
Employees would still have to work their full hours to receive their full pay but could compress their contracted hours into a shorter working week.
Conservative shadow business secretary Kevin Hollinrake claimed businesses were “petrified” about the plans.
However, ministers insist they will not impose the change on staff or businesses.
“Any changes to employment legislation will be consulted on, working in partnership with business,” said a spokesperson at the Department for Business and Trade.
They added that the plan for more flexible working was instead designed to increase productivity and help get more people back into work.
Currently, employees have the right to request flexible working but employers are only required to deal with requests in a “reasonable manner”.
Labour came to power earlier this year promising to make it the default from day one for all workers, except where it was not feasible.
As first reported by the Daily Telegraph, that could allow staff to work four longer days instead of five.
Details are expected in the autumn when a law to create a new package of workers’ rights is expected to begin its journey through Parliament.
Labour has pledged to repeal some anti-trade union laws, restrict the use of zero-hours contracts and expand flexible working arrangements.
Prime Minister Sir Keir Starmer calls the proposals “the biggest upgrade to workers’ rights in a generation” and Deputy Prime Minister Angela Rayner argues they will be “good for the economy”.
But the Conservative opposition claims the approach would damage business and lead to reduced productivity.
“Despite warning after warning from industry, Angela Rayner is pressing ahead with her French-style union laws that will make doing business more expensive in the UK,” Mr Hollinrake said.