Defence Minister Mosiuoa Lekota has vowed to co-operate fully with the public protector's investigation into his undeclared assets and said he would accept any sanction that follows.

Public Protector Lawrence Mushwana said on Thursday that the investigation into the Lekota matter, conducted in terms of the Executive Members Ethics Act, was progressing.

The investigation should be completed by the end of the month, Mushwana added.

Once the investigation was complete, a report would be given to President Thabo Mbeki, who would decide whether to impose any sanction on Lekota.

This could be a harmless slap on the wrist - or a dismissal, but that is unlikely.

Lekota has been fined a week's salary and received a written reprimand from National Assembly speaker Frene Ginwala for failing to declare some of his financial interests.

Parliament's joint committee on ethics and members' interests, which imposed the penalty, found recently that Lekota had failed to comply with the provisions of parliament's code of ethics with regard to financial interests, and that he had been "negligent in making incomplete disclosures of his interests".

However, it added there had been no evidence that Lekota had wilfully withheld information with the intention of misleading parliament.

In terms of the ethics code, MPs must declare gifts worth more than R350 and any directorships or shares they hold in companies.

Lekota said he accepted full responsibility for the fact that he had failed to declare some of his business interests in parliament's register of members' interests.

Speaking at a defence force media briefing on Thursday, the minister said he had accepted that he had been negligent in failing to declare some of his interests.

"I should have paid more attention" rather than charging his staff with certain responsibilities, he added.

Nonetheless, he accepted full responsibility for his actions and the punishment imposed by parliament.

"I accept that I am wrong. I am sorry I committed this mistake," Lekota said.

He pointed out that he had co-operated fully during the investigation by parliament's ethics committee.

Lekota said he was ready to appear and give evidence before the public protector. He added that he would accept the result of the investigation, whatever the outcome.

The defence minister said he held the view that "you cannot build a house from the ground to the roof without getting splattered with mud". Lekota must also face an internal disciplinary committee of the African National Congress.

He has admitted that he failed to disclose a 33 percent share in Prestprops 1169 and a 5 percent share in Prestprops 1209, which trades as BZL Petroleum.

He also failed to disclose his directorship of BZL, directorship of Landzicht wine cellar and directorship of GWK.

With acknowledgements to Andre Koopman and The Star.