Marks & Spencer's admission that it pays its female staff 12.3% less than male workers has reignited the gender pay gap debate.

The retailer has attributed the gap to the fact that senior management roles are mainly held by men. Men only make up 28% of M&S' workforce, but hold around 57% of its senior positions and constitute 70% of the 10-person board.

The company revealed on Tuesday (27 February) that its mean gender pay gap is 12.3%, while the difference in bonuses awarded to male and female staff was 53.4%.

M&S said the mean gap was lower than the national average of 17.4%, but admitted more could be done.

"We recognise there is more to do to close the gap – we are focusing on addressing our pipeline of women into senior roles as well as encouraging more flexible working," the company said in a statement.

It said that future job adverts will encourage people applying to ask about flexible hours to highlight that it is an "important part of our culture."

"We want to make sure everyone has the opportunity to ask about this and to show it is an important part of our culture," M&S chief executive Steve Rowe said.

He added that M&S will provide mentoring to women in mid-senior levels looking to progress in their career.

"The issues at play are complicated, and we believe it's much more important to focus on taking meaningful action to drive equality and inclusivity rather than simply the numbers themselves," said Simmone Haywood, the retailer's head of talent.

Over 1,000 companies have so far published their gender pay gap reports, after the government made it compulsory for all organisations with more than 250 workers to present annual reports.

Among the retailers, clothing chain Phase Eight has one of the largest gender pay gaps, with its hourly rate for female staff on average 64.8% lower than that paid to men.

Last year, the Bank of England revealed that its male workers were paid 24% more than female staff on average, citing the low number of women in senior positions as the main reason for the gap.