The call comes from Amicus, one of the UK's largest trade unions, as part of its campaign to close the pay gap between men and women.

There is no reason for any company to refuse to carry out an equal pay audit unless it is to conceal discrimination against women in the workplace and that is against the law Fiona Farmer, Amicus equalities officer

The union has claimed that female workers earn 29% less than their male colleagues despite the Equal Pay Act.

As part of the campaign Amicus has said that male union members should sign an equal pay charter which supports strike action if employers refuse to conduct equal pay audits to uncover where and how pay gaps appear.

Law breaking

According to Fiona Farmer, the Amicus equalities officer, the equal pay issue is often overlooked by men who see it as a women's problem rather than one of wider worker rights.

"This campaign is asking men whether or not they think their family can afford to have one of its incomes cut by up to 29% when the Christmas credit card bills start landing on the doormat," she said.

The union would like to see the government legislate to make firms carry out regular equal pay audits to discover if female staff are lagging behind in the wages stakes.

"There is no reason for any company to refuse to carry out an equal pay audit unless it is to conceal discrimination against women in the workplace and that is against the law," Ms Farmer said.