British workers will carry out £23 billion in unpaid overtime this year, the TUC has claimed.

Union leaders launched their latest initiative on Monday aimed at calling a halt to the "long hours culture".

Its latest report, which is part of its campaign against long working hours, confirmed again that Britons work the longest hours in Europe.

Around five million people work an average of seven hours 24 minutes extra each week without pay on top of the minimum 48 hour week recommended by the EU.

The TUC claims that adds up to an extra £4,500 each a year.

Among professional staff that rises to an extra nine hours 36 minutes a week extra - which amounts to £9,000 per individual a year.

"Britons work the longest hours in Europe, and these figures show that much of it is unpaid overtime," said TUC general secretary Brendan Barber.

"We're not saying we should turn into a nation of clock-watchers, or that no-one should put in extra work when there's an emergency or a rush of orders, but many people are clearly putting in the equivalent of an extra day every week."

Barber argued the long hours culture has become a key part of preventing more women taking top jobs.

"Is it any wonder that top jobs are still dominated by men, when managers have to do an extra day's unpaid work each week?" he asked.

"When employers quote dubious figures about the costs of what they call red tape, and everyone else calls basic rights at work, do they remember their staff put in billions of pounds worth of unpaid extra work each year?

"Given that workers in much of the rest of Europe work fewer hours, yet produce and earn more, are there not hard questions to ask about the quality of UK managers?''

But business leaders rejected the TUC's claims, saying they had presented a skewed picture of employee attitudes to working time.

"In reality the unions not only dislike unpaid overtime, they also want to limit paid overtime by removing the right to opt out of the working time directive," said John Cridland, deputy director general of the CBI.

"Whether paid or not, the message seems to be 'we know best' on the number of hours people should work. The fact is most people do extra hours because they want to."