The Equal Opportunities Commission (EOC) has set up a task force to tackle the problem, backed by a nationwide advertising campaign.

Employer and union representatives will join the task force to study the pay gap across the UK, before making recommendations later this year on how to close it.

The first of a series of adverts appeared on Tuesday, with the message: "Prepare your daughter for working life - give her less pocket money than your son."

EOC chairwoman Julie Mellor said that, apart from a 1% narrowing of the pay gap brought about by the national minimum wage, little progress have been made since equal pay laws were first introduced 30 years ago.

Not widely recognised

She said: "Equal pay is a principle whose time has come.

"It is no longer acceptable that women are only paid 80% of what men earn."

Research for the EOC showed that most 17 to 25-year-olds were unaware of the pay gap.

More than 70% of young women surveyed said an employer's commitment to equal pay would influence their job choice.

Ms Mellor said: "This research represents a wake up call for the country. The cream of British youth simply won't stand for the gender inequalities we've all put up with for too long."

The average weekly wage for women is £326.50, while men earn an average of £442.40.

Low-paid jobs

Average hourly pay for women is 80.9% of that for men - up from 63% when the Equal Pay Act was introduced in 1970.

The pay gap partly reflects the differences in women's and men's occupations.

There are many more women in low-paid clerical jobs, while there are more men in higher-paid management posts and in factory jobs.

Working women are also younger on average than men, reflecting the fact that many leave the workforce to raise children.

However, even where these differences do not exist, there is often disparity between men and women's pay.