UK firms with over 250 employees have until midnight tonight to report their gender pay gaps.

Many firms have already published their gender pay gap data. According to The Guardian, more than 9,000 employers have already filed their gender pay gap report. The deadline for public sector employers to file the gender pay gap reports was Friday with data showing that 1,643 public sector employers have fulfilled the requirement.

Among the companies with the biggest pay gap was Ryanair which had the worst record for paying women less than men in the entire UK aviation sector. The company revealed a gender pay gap of 72%. Ryanair stated that the discrepancy was due to the relatively low number of female pilots compared to those in cabin crew as pilots are paid far more than cabin crew.

The BBC reported that Prime Minister Theresa May said the gender pay gap disclosures would make for "uncomfortable reading", but said it was vital the "burning injustice" was tackled.

"It is essential that we do so,” May said. “Most importantly, because equality for women is a right, and our whole society is the poorer as long as it remains unrealised."

Carolyn Fairbairn, Confederation of British Industry Director-General, commented, “There’s nothing more important for firms than attracting and retaining the best possible people. Companies want to close the gender pay gap.  They have plenty of good practice to draw on – from great flexible working policies, to widening recruitment and engaging with schools to inspire young women into STEM subjects."