According to the report by the Trades Union Congress (TUC), Britons put in an average of 43.6 hours weekly, compared to the Europe-wide average of 40.3, Reuters said.
One in six working Britons puts in longer than 48 hours, a limit set by a European working time directive that became British law in 1998, the report said.
The report found that 70% of skilled and manual workers put in extra hours to earn overtime pay.
Many European countries already have much tougher restrictions on working hours, according to the Reuters report.
Workers Austria, Belgium and Sweden have 39- or 40-hour limits, and France has a 35-hour week. However, figures gleaned separately from the TUC research showed that French workers are 24% more productive than Britons on an hourly basis and Germans 11%.
Britain is the only EU state that allows employees to opt out of the bloc’s working hour limit if they want to. But this clause would be reviewed by the European Commission by 2003, the TUC report said, and was likely to be removed.