LONDON, May 26 (Reuters Life!) - The average Briton turns up to work with a hangover three times a month, according to a survey on Wednesday, and the frequency is expected to increase during next month's World Cup.

The charity Drinkaware found each day more than 520,000 people in Britain go to work hung over, with nearly one in five of those admitting that as a result they make mistakes and struggle to keep on top of their workload.

"An international sporting event like the World Cup will inevitably capture the attention of the nation and is a great time for people to come together, but hangovers at work are likely to increase," said Drinkaware Chief Executive Chris Sorek.

"With hundreds of thousands of people going to work every day after a heavy night, it impacts work productivity and even results in employees going home sick."

While nine out of 10 people said they considered having a hangover at work unacceptable, two-thirds of the 1,085 adults questioned by pollsters ICM admitted they had joked with their colleagues or boss about having a hangover.

Of those who went to work hung over, seven percent have had to leave work early because they were too ill to carry on.