Europe has made little progress over the past decade towards ending sexual discrimination in the job market, the European Commission says.
Jobs dominated by women are traditionally less well paid
Women still earn 15% less than men on average, compared with 17% in 1995, despite being better educated.
In some states, including Germany and Finland, the pay gap has grown.
Employment Commissioner Vladimir Spidla said it was "an absurd situation" that required changes to employment policies and better application of existing law.
The pay gap is at 20% or above in six countries: Finland, the UK, Germany, Slovakia, Estonia and Cyprus.
"There is nothing to indicate that this gap is narrowing in any significant way," says a commission report published on Wednesday.
Growing with age
"It is an unacceptable waste of resources for the economy and society which prevents the productive potential of women from being fully realised."
The commission wants the 27 member states to set objectives and deadlines to eradicate the gap, and will also push for equal pay to be made a condition for winning public contracts.
Statistics show that the pay gap grows with age, education and years of service. It is:
- More than 30% in the 50-59 age group, compared with 7% for the under-30s
- More than 30% for those with higher education and 13% for those with lower-level secondary education
- As high as 32% for workers with more than 30 years of service in a company, compared with 22% for those who have worked in a company for one to five years
One reason the pay gap is high in the UK and Germany is the high proportion of women in part-time work - more than 40% in both countries, compared to an EU average of 31.2%.
Other problems identified by the commission are a "glass ceiling" that makes it harder for women to get top jobs, family responsibilities and the fact that jobs traditionally dominated by women are less well paid.
"The gender pay gap extends well beyond the question of equal pay for equal work," the commission says.
"One of the main causes is the way women's competences are valued compared to men's. Jobs requiring similar qualifications or experience tend to be paid less when they are dominated by women than by men."
The countries with most women in management positions are Latvia, Lithuania, France and Hungary, with the UK in fifth place. Denmark, Malta and Cyprus had fewest women managers.
Yet women make up 60% of the EU's university graduates.