Cosatu in the Western Cape want Premier Helen Zille and the DA probed following reports of alleged overcharging for Cape Town construction projects, it said on Monday.
"Cosatu calls on the Competition Commission, Public Protector and Public Service Commission to investigate Helen Zille and the construction of the IRT bus system routes in Cape Town, in addition to the stadium, due to persistent allegations of corruption and price fixing," the union federation's Western Cape leader Tony Ehrenreich said.
Zille and the Democratic Alliance should be included because she was premier at the time contracts were awarded.
In addition questions had been raised in recent media reports over the party's funding sources, Ehrenreich said.
The Cape Argus reported that the Hawks were probing allegations that the City of Cape Town was overcharged for the Cape Town stadium through alleged collusion between construction companies.
The Competition Commission had also advised the city it would convene a public tribunal to hear the allegations.
The two-pronged investigation followed the commission's announcement in 2011 that the stadium was one of many construction projects around the country being probed for alleged bid-rigging.
It said at the time it was investigating 65 cases involving 70 projects worth about R29-billion after "uncovering widespread anti-competitive conduct through various arrangements" in the industry.
The stadium's initial price was R2.9-billion, but it ultimately cost more than R4.3-billion.
Cape Town spokesperson Kylie Hatton told the newspaper if the allegations were proved true, the city could take a number of steps, including legal action to recover costs, a formal civil claim, and/or officially blacklisting any party found guilty.
The Congress of SA Trade Unions (Cosatu) wanted criminal charges to be laid against the directors of the construction companies, and jail terms for guilty parties.
Ehrenreich said: "The amount of money going to the DA fundraising is exceptional, as reported by many sources."
Zille was embroiled in a controversy after the party received funding from an individual connected to the Gupta group, which owns The New Age newspaper.
This followed an earlier controversy over the newspaper itself receiving public money to pay for its business breakfast broadcasts.