Allen & Overy (A&O) is declining to provide MPs with its 2016-17 partnership gender pay gap figures, after a UK parliamentary select committee wrote to the entire magic circle asking them to do so.

Chair of the Business, Energy and Industrial Strategy Committee, Labour MP Rachel Reeves, wrote to all five magic circle firms last month to request the breakdown of gender pay gap data including partners.

Clifford Chance and Linklaters had already published their data earlier this year and provided it again to the committee, while Freshfields Bruckhaus Deringer and Slaughter and May gave the committee the breakdown when asked. A&O, however, has declined to provide the information, with the story first reported on RollonFriday.

While neither Freshfields nor Slaughters are publicly revealing their gender pay gap data at this point, the firms' letters to the committee containing the information will be published.

Freshfields has also confirmed that it will include partner data in its gender pay gap reporting next year and will also publish restated figures for 2016-17, including partners, at the same time.

A&O told Legal Week that it will provide the select committee with a gender pay gap figure including partners for the 2017-18 financial year by September. A spokesman said the firm had not yet decided whether it would release the data for the 2016-17 year.

All of the UK top 50 law firms reported their gender pay gap data earlier this year in compliance with UK regulations, which do not require them to provide partnership data.

A&O's gender pay gap report revealed that more than 25% of its London staff are women in business support roles, and that 71% of employees in the firm's lowest-paid quartile are female – an imbalance which means that average hourly pay for male staff is 19.8% higher than for women and average bonuses for men are 42.1% higher.

At the time, the firm acknowledged that it had "not succeeded in retaining and promoting enough" of its best women, stating that it has put strategies in place – including creating a gender advisory committee – to ensure it is making progress.

This year the firm promoted just two women to partnership, as it continues to struggle with the challenge of meeting gender diversity targets for its senior ranks.