Chair of the Treasury Committee Nicky Morgan MP has written to asset managers including PIMCO, JP Morgan Asset Management (JPMAM) and Vanguard and 30 other financial services firms to ask why they have not signed up to the Women in Finance Charter.
Other asset managers the Treasury indicated have not yet signed up include Invesco Perpetual, Amundi and Close Brothers.
However, Goldman Sachs Asset Management (GSAM), Invesco Perpetual and Close Brothers confirmed to Investment Week they are in the process of signing up, indicating it will be announced with the next Women in Finance Charter (WIFC) communications in March.
Invesco said: "Our firm has received a letter from the Treasury Select Committee. The Treasury will be announcing the next group of Women in Finance Charter signatories in March and our firm will be on that list."
A statement from GSAM said: "At Goldman Sachs we are committed to promoting diversity and inclusion at all levels of the firm. It is critical that we recruit and retain a diverse group of people who bring a broad range of experiences, capabilities and perspectives to our organization. Our participation in the Women in Finance Charter is one element of this broader commitment."
The Treasury Select Committee launched an inquiry into Women in Finance Charter on 19 October 2017 to explore the barriers that women entering and progressing their careers often face in the financial services industry.
So far achieved 162 signatories have signed up, HM Treasury estimates represent over 600,000 employees in the industry, which is around half of the employees in the financial services sector.
However, chair of the Treasury Committee Morgan is concerned that a number of key players have yet to commit to the initiative.
A statement from Morgan said: "The progress of the Women in Finance Charter is to be welcomed. The aim, however, must be to see all firms in the financial sector sign up to the Charter and make a concerted effort to improve their gender diversity, particularly in senior roles.
"As the Charter states, a balanced workforce is good for customers, profitability and workplace culture.
"Huge multi-nationals including Goldman Sachs, JP Morgan and UBS are yet to sign up to the Charter, and if they don't intend to do so, the Treasury Committee wants them to explain why."
Her letter to the groups asks them to explain why it has not yet signed up. It said: "The Committee understands that your firm has yet to sign the Women in Finance Charter. I would be grateful if you could write to the Committee by 16 February 2018, setting out whether you will sign the Charter with the next cohort of signatories and if not, the reasons why you are not signing up to this initiative."
Confirming they are committed to the initiative, Close Brothers' statement said: "We are strongly committed to supporting gender diversity and equality across the organisation and our chief executive is a longstanding member of the 30% Club, an institution aimed at promoting gender balance at all levels.
"As part of our membership commitments, we have already agreed to work towards an aspirational target of a 30% female representation among our senior management population and have a number of commitments and initiatives in place to meet this target.
"We already exceed the government's target of 33% of boards being women, and are in line with the Hampton-Alexander gender targets for executives and their direct reports.
"We are therefore completely supportive of the principles of the Women in Finance Charter and have signed up."
A JPMAM spokesperson said it "supports the goals of the charter and is considering signing up," while Vanguard is also considering its position.
A spokesperson for Vanguard said: "As a signatory to a number of industry groups that promote diversity, Vanguard is committed to advancing the importance of gender diversity in the financial services industry. We are currently evaluating the opportunity to add our name to the Charter."
Meanwhile, Amundi and PIMCO said they were unable to comment at this stage. However, PIMCO highlighted diversity is an issue they are committed to with the firm being a founding member of the CFA Gender Diversity Programme.