Women were paid 21 percent less in Germany than men last year, leaving the gender pay gap in Europe's biggest economy unchanged, the Federal Statistics Office said on Thursday.

Men earned on average 21.00 euros ($26) an hour in 2017, compared with 16.59 euros for women, the Office said. In 2007, the gap was 23 percent.

The figures were released ahead of Germany's Equal Pay Day on March 18, calculated as the day until which women symbolically work for free each year before they start earning the same as men.

Germany is one of the biggest sinners on equal pay in the European Union, where women on average earn 16 percent less than their male peers.

Only Germany, Britain, the Czech Republic, Austria and Estonia recorded wage gaps above 20 percent in 2016, the bloc's statistics agency Eurostat reported last week.

The best performers were Romania, Italy and Luxembourg with gaps of around five percent.

As part of its efforts to tackle the imbalance, Germany in January introduced new legislation that gives women the right to know how their salary compares to that of a group of male colleagues in the same job.

The hope is that more transparency will reveal whether women are paid less — and bolster their demands for a rise or pave the way for possible legal action.

Critics however complain that the law, which only applies to firms with more than 200 employees, will only foster workplace discontent as it doesn't force bosses to take action against wage discrepancies.

The Federal Statistics Office said the difference was explained partly by where men and women tend to work. Other factors were fewer women being bosses and more women than men holding part-time jobs, it said.

A so-called "adjusted" gender pay gap for men and women in comparable jobs and with comparable qualifications was about 6 percent.

For women with the same qualifications doing the same work as men, the pay gap stands at around six percent.

The overall gap is roughly three times as big in western Germany, at 22 percent, as it is in the former Communist East, where it is 7 percent.