The Public Service Commission (PSC) says it will probe Public Service and Administration Minister Faith Muthambi - just days after the Portfolio Committee on Communications resolved to investigate her.

While the portfolio committee will look into Muthambi's conduct in her previous post as communications minister, the PSC will look into allegations that she had expanded her private office to include 40 staff members - including some family members and friends. Muthambi has previously denied any wrongdoing.

Democratic Alliance MP Desiree van der Walt laid a complaint last Friday and by Tuesday, PSC chairperson Richard Sizani responded via a letter, stating that they will investigate the regularity of the filling of the posts.

Sizani warned Van der Walt that the PSC face budgetary constraints, but added that the commission "will nevertheless prioritise the member's request within its human and financial constraints".

Van der Walt welcomed the PSC's decision.

"For far too long, Minister Muthambi has 'got away with murder' in her brazen attempt to turn the ministry into an employment agency for the politically connected few. Money that could have been better spent creating a more accessible public service was diverted to hire excess food aides, drivers and administration assistants," she said.

"Minister Muthambi's behaviour has been enabled by an ineffectual leader of government business, Cyril Ramaphosa, who has turned a blind eye while the rot festered."

On Tuesday, the portfolio committee undertook to bring finality to "the implementation of recommendations of the Ad Hoc Committee on the South African Broadcasting Corporation (SABC) Board Inquiry in relation to the former Minister of Communications, Ms Faith Muthambi."

It said the matter was serious and should be finalised urgently.

The ad hoc committee found Muthambi to be incompetent as the communications minister and found that she could have contravened legislation, including the Constitution.

Furthermore, Parliament's legal services said that Muthambi's testimony before the committee "could be seen as an attempt to mislead the inquiry".