ALMOST £600m was lost to workers in the North-East through unpaid overtime last year, says the TUC.
The organisation said that nearly 150,000 employees in the region would have earned £4,051 each for their unpaid hours if they were paid at their normal hourly rate.
In Yorkshire and Humberside workers put in unpaid overtime worth £1.8bn.
The TUC has nominated February 25 as Work Your Proper Hours Day and is urging people to work only their contracted hours to remind bosses how they depend on unpaid extra work and staff loyalty.
TUC general secretary Brendan Barber said: "We are not saying that we should turn into a nation of clock-watchers.
"Most people do not mind putting in some extra time when there is a crisis or an unexpected rush, but too many workplaces in the North-East have come to depend on very long hours.
"They get taken for granted and staff have to do even more if there is an unexpected rush.
"Worst of all is that many long hours workplaces are inefficient and unproductive.
"People are putting in long hours to make up for poor organisation and planning in the workplace."
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