BRITISH workers are handing bosses a massive £33.6 billion a year in free labour through unpaid overtime, new research shows today.

Analysis of official statistics reveals that 2.1 billion hours were worked without pay last year.

The TUC urged workers yesterday to take proper lunch breaks and leave on time as part of its annual Work Your Proper Hours Day.

Some 5.3 million people put in an average of 7.7 hours a week in unpaid extra hours, TUC data shows.

London-based staff and public-sector workers are statistically more likely to be affected by presenteeism and are under more pressure to put in extra slog for no reward.

TUC general secretary Frances O’Grady said: “Few of us don’t mind putting in some extra time when it’s needed, but if it happens all the time and gets taken for granted, that’s a problem.

“So make a stand today, take your full lunch break and go home on time.

“Anyone worried about the long hours culture in their workplace should get together with workmates and join a union. That way, you can get your voices heard and get the support you need to make sure your boss doesn’t break the rules.”

More than 1.6 million British workers are doing so much unpaid overtime that they exceed the 48-hours-a-week limit of the EU Working Time Directive, the figures show.

The TUC has warned that this directive and other employment protections will be at risk when Britain leaves the European Union and has called for equivalent or greater safeguards to put in place.

However, Britain “ops out” of the 48-limit, which employees can exceed if they give consent — a loophole leaving workers open to pressure by bosses.

Teachers were disproportionately affected by the explosion in unpaid overtime, according to the TUC study.

“This situation is untenable,” National Union of Teachers general secretary Kevin Courtney said. “Long and unmanageable working hours are the biggest single reason cited by teachers for leaving the profession.”

University and College Union general secretary Sally Hunt said: “The time has come for schools, colleges and universities to recognise the hard work their staff do, reward them fairly and sort out their workloads.”

Labour’s shadow business secretary Rebecca Long-Bailey said: “Although staying late is sometimes necessary, the long-hours culture is neither good for workers or businesses.

“Overwork never produces good results for employees or firms, not to mention the impact it has on physical and mental health.

“This is also an important reminder that we need to ensure working-time protections are safeguarded in the Brexit negotiations.”