New allegations of impropriety against one of men at the centre of South Africa's billion-dollar arms deal, prompted calls on Sunday for investigations into state tenders and into the funding of the ruling African National Congress.

The Democratic Alliance will ask the Public Protector and the Auditor General to probe business dealings between former Transport Minister Mac Maharaj and Durban-based businessman Schabir Shaik.

Shaik is under investigation by the Scorpions for his role in the billion-rand arms deal.

DA transport spokesman Stuart Farrow said in a statement on Sunday that the dealings between the two men appeared to be "fraught with favouritism and bribery".

The Sunday Times reported on Sunday that Maharaj and his wife Zarina received R500 000 from Shaik -- most of it before Maharaj left the cabinet in 1999.

The newspaper said it was in possession of documents that show Shaik or his companies deposited amounts ranging from R10 000 to R75 000 into the accounts of Maharaj and his wife between 1998 and 2000.

Shaik, who is the personal financial adviser to Deputy President Jacob Zuma, is the chief executive of Nkobi holdings and a director of Nkobi investments.

Nkobi investments is part of the N3 Toll Road Consortium, which was awarded a R2,5 billion tender to upgrade the road from Johannesburg to Durban by the Department of Transport while Maharaj was the minister.

A Nkobi Holdings subsidiary, Kobitech, is part of the consortium Probida, which won a R265 million contract to produce new credit-card driver's licences.

United Democratic Movement leader Bantu Holomisa, meanwhile, called for the appointment of a judicial commission of enquiry to probe the African National Congress's sources of funding, claiming that the ruling party was using "bogus" companies and consultants to raise money.

Holomisa said such an inquiry should "find out how much money of the state has been channelled back to ANC coffers through these bogus companies and consultant like Nkobi ... these companies were established by the ANC".

"It is clear that the ANC and its leaders are looting the resources of the state through these companies," he said.

Farrow said the DA would ask the Public Protector and the Auditor General to focus on why Maharaj did not disclose the payments in terms of parliament's register of interests.

Other outstanding questions were which bidders for the N3 toll road contract were disadvantaged by the awarding of the contract to the N3 Toll Road Consortium and who were the directors of the consortium.

The DA would also ask President Thabo Mbeki to question the validity of contracts signed by Cabinet during Maharaj's tenure.

"Particular attention should be paid to the recommendations and arguments presented by Mr Maharaj on the awarding of these two tenders," Farrow said.

The DA would also ask if Maharaj was bound by Cabinet's code of conduct and if so, what were the consequences of his allegedly not declaring gifts or favours he received.

On Saturday, Maharaj declined to comment on the payments or on his relationship with Shaik.

It is believed that the Scorpions' investigation of Shaik has been extended to include Maharaj and a number of government officials, but Scorpions spokesman Sipho Ngwema said would not comment on this.

With acknowledgement to Sapa.