Parliament's ethics committee has given former African National Congree chief whip Tony Yengeni a belated tongue-lashing for damaging public trust in the institution and plans to rethink the code of conduct for MPs in the wake of the scandal.

In a statement issued on Friday the Joint Committee on Ethics and Members' Interests firmly rebuked the disgraced former MP following his admission of guilt on charges of defrauding parliament by not declaring the 47 percent discount on his luxury Mercedes-Benz 4x4.

Yengeni resigned from parliament last week under pressure from the ANC leadership, but not before the party suffered embarrassing publicity over his refusal to quit.

"The committee deplores, in the strongest terms possible, the damage done to public trust in parliament by Mr Yengeni," chairperson Lewellyn Landers said in the statement after a meeting of the committee.

According to the statement, MPs were "expected to display the highest standards of propriety" and "any deviation from those standards of ethical behaviour by members, results in the erosion of public trust in parliament".

MPs were also "expected not to take any improper advantage or benefit by virtue of the office they hold".

The committee also found, given Yengeni's guilty plea in court, "that his continued participation in parliament would have been inappropriate". His resignation was therefore "appropriate".

Democratic Party chief whip Douglas Gibson said he was satisfied that the committee had done what it could to rebuke Yengeni, given that it did not have any jurisdiction over Yengeni since his resignation.

However, he said, parliament would have to process the Powers and Privileges Amendment Bill as a matter of urgency to avoid a situation where, as with the Yengeni case, the ethics committee found itself powerless to take firm action against MPs in such serious cases.

Parliament currently does not have the power to expel MPs, but can publicly rebuke, fine or suspend them.

Inkatha Freedom Party MP Sybil Seaton said a committee decision to rethink the code of conduct for MPs and its investigation powers was an important step forward.

Landers, the committee chair, told Saturday Star that the Yengeni case had highlighted the fact that the code of conduct was not clear on the issue of discounts. Also, the committee needed wider investigation powers.

With acknowledgements to Jeremy Michaels and Saturday Star.