The European Union on Tuesday adopted "landmark" legislation aimed at increasing the number of women on the boards of big companies in the bloc.

EU lawmakers meeting in Strasbourg signed off on the long-awaited measures after 10 years of negotiations within the bloc.

The new rules seek to have at least 40 percent of non-executive director posts or a third of all director posts on publicly listed firms filled by women by July 2026. 

"This is a long-awaited moment, a moment to be celebrated as a breakthrough in gender equality," the European Commission, the bloc's executive arm, said in a statement.

"We will now have an EU law to break the glass ceiling of listed companies boards."

The EU says that, on average across the 27-nation bloc, just 30 percent of board members in companies are women.

That figure varies dramatically between member states, ranging from 45 percent in France to eight percent in Cyprus. 

Currently, fewer than one in 10 of the largest firms in Europe have a woman as their top boss. 

The new regulations require EU member states to impose "effective" penalties for companies that do not reach the targets, including fines or being publicly named and shamed.

Under the rules "merit must remain the key criterion in selection procedures" and listed firms will have to provide annual updates of the gender balance on their boards. 

Companies with fewer than 250 employees will be exempt from the regulations. 

"We are finally giving women a fair chance to be in top corporate positions," said Austrian MEP Evelyn Regner, who spearheaded the push for new regulation.

"We are removing one of the main hurdles for women to get the 'top jobs': informal male networks. From now on, competence will count more," she said.