LONDON, March 8 (Xinhua) -- British industry celebrated International Women's Day Thursday by announcing a record number of women now serve on the boards of the top 100 companies.

But figures released by the Department for Business, Energy and Industrial Strategy (DBEIS) show it could be 2020 before a third of boardroom positions are held by women.

Analysis published to mark International Women's Day by the leading organization representing works, the Trades Union Congress (TUC), said gender pay gaps in the workplace effectively mean women in Britain work an average 67 days a year for free.

Government Business Minister Andrew Griffiths urged businesses to renew their commitment to tackling gender inequality.

New data reveals that a record 309 women serve in on FTSE 100 boards, and a quarter of FTSE 350 board positions are now filled by women

In FTSE 350 companies, the number of women chairs has risen from 17 to 20 while the number of women on boards has increased to 25.2 percent.

Business Minister Andrew Griffiths said: "I am delighted to see that a record number of our largest companies' board positions are now filled by women. There has been a lot of progress in recent years with high-flying women breaking down barriers but there is still a lot more to do to ensure that women are not held back in the workplace."

Under new laws in Britain over 1,400 companies have reported their gender pay gaps revealing an overall pay gap of 18.4 percent, said DBEIS.

All companies with more than 250 employees must report their gender pay gaps by April 4 or March 30 for the public sector.

Meanwhile an analysis published Thursday to mark International Women's Day by the TUC has revealed that the average woman has to wait more than two months of the calendar year before she starts to get paid, compared to the average man. It means women effectively work for free for 67 days of the year compared to men because of the gender pay gap.

"In some industries, where the gender pay gap is even bigger, women work for free for even longer and have to wait until April or even May for their Women's Pay Day," said the TUC.

The TUC, now headed by its first ever female general secretary Frances O'Grady said: "Britain still has one of the worst gender pay gaps in Europe. Women effectively work for free for two months a year.

"Companies publishing information on their gender pay gaps is a small step in the right direction but it's nowhere near enough. Women in the UK will only start to get paid properly when we have better-paid part-time and flexible jobs."