Germany's Bundestag is expected to adopt a quota on Friday for women in the country's boardrooms.

The law will make it compulsory for the non-executive boards of at least 108 German companies listed on the stock market to be made up of at least 30 percent women. From 2016, these companies could be penalized if they do not comply with this quota.

The quota was negotiated near the end of 2013, but a formal accord among Germany's three-party grand coalition was not reached until a year later. Chancellor Angela Merkel's cabinet approved the plan in December.

Small businesses will also be required to take steps to improve workplace equality, with the quota being introduced on a sliding scale in terms of the size of the company. From 2017, smaller companies and public services must report on their progress in increasing the number of women in leadership positions, but they will not be penalized if they do not meet the quota.

The Minister of Family Affairs, Manuela Schwesig, said the quota was historic.

She told the Passauer Neue Presse newspaper it was "important that, finally, more women are put into executive positions."

"Women will see what is possible," Schwesig said.

The proposal has been a bone of contention among some members of Chancellor Merkel's grand coalition. Merkel's conservative Christian Democrats (CDU) - and their Bavarian sister party the Christian Social Union (CSU) - have resisted legal quotas in the past. Other critics, such as business and industry groups, worry the law will have detrimental economic effects if certain companies are not exempted.

The proportion of men in German boardrooms is still at over 80 percent, despite roughly 40 percent of the federal cabinet being female. According to the DIW economic think-tank, women occupy just 7 percent of executive board seats among the 30 largest companies on Germany's blue-chip DAX index.

jr/gsw (dpa, epd)