UK teachers work more than a day of unpaid overtime every week, the most of any sector, according to new analysis.

The Trades Union Congress (TUC), which carried out the research, said that amounts to 9 million hours of free labour a week, or 462 million hours a year.

According to analysis of official data by the unions’ umbrella body, teachers work an average of 12.1 hours unpaid every week.

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Primary teachers work the most, at 13 hours, just more than the 12.8 hours put in by secondary teachers and over twice the 6.4 hours in pre-school.

That’s more than chief executives, lawyers, hospitality and catering managers and ‘functional’ managers in finance, marketing or personnel.

Taking the profession as a whole, the TUC calculated that is equivalent to 735,000 teachers working overtime without pay every year.

The body says that is almost 10 times as much as legal professionals and nearly 15 times more than welfare professionals.

“Teachers top the list for unpaid overtime,” said TUC general secretary Frances O’Grady.

“Our education system can’t be run off the back of free labour and goodwill. The government must tackle staff shortages and overwork by giving schools the resources they need.

“Ministers need to work with teaching unions to address the unacceptable workloads that are driving so many dedicated teachers out of the profession.”

Kevin Courtney, joint general secretary of the NEU teaching union, said much of this overtime is "spent evidencing the work they are doing".

"Teachers say many of the hours they are being expected to do aren’t even helpful to the children they teach," he said.

"With workload going up and real terms pay going down it is no surprise that we are facing such problems with recruiting new teachers and keeping the ones we’ve got.”

The TUC’s analysis echoes numerous studies highlighting how British teachers’ workload is driving them out of the profession in droves.

This week new research found more teachers feel tense or worried about their job than in other comparable professions.

A study released in November found British teachers work some of the longest hours in the world.

The Department for Education has pledged action to cut teachers’ workload in a bid to quell the recruitment and retention crisis.