The Trades Union Congress (TUC) has called on UK employees to work no more than their contracted hours today, claiming that employers get £23 billion of ‘free’ work a year through unpaid overtime.

The TUC has designated today ‘Work Your Proper Hours Day’ and has urged all staff to stick to their regular hours to remind bosses “how much modern workplaces depend on their unpaid overtime.”

According to the trade unionists, employees working in agriculture, production and textiles undertook the longest periods of after-hours work.

The TUC compiled a calendar showing the dates that various employees effectively stop working for free. Agricultural workers will start earning on 19 March, while production staff’s unpaid overtime stretches to 9 March.

Care home managers will start earning from today, while telephonists’ unrewarded overtime ended on 19 January.

Trade union leaders have repeatedly criticised the UK’s ‘long hours culture’, which sees British employees work the longest average week in Europe.

The TUC has claimed that long hours damage productivity and staff health, and has urged the government to fully adopt the EU Working Time Directive, which limits workers to a 48-hour week.

However, business groups have argued that employees should have the right to choose how long they work for, including overtime.

Brendan Barber, general secretary of the TUC, said that he was not calling on Britain to turn into a nation of clock-watchers.

“But too many of Britain’s bosses who depend on the unpaid overtime of their staff take it for granted and never show their appreciation.

“That’s why we’re saying that for one day a year people should make an effort to work their proper hours.

“They should come in on time, take their proper lunch break and leave when they are meant to, preferably on their way to somewhere where their boss will buy them a coffee or a cocktail,” he said.