Tony Ehrenreich, Cosatu's Western Cape secretary, accused the DA-controlled council of using complaints about the disused and dilapidated army base in the up-market suburb of Tamboerskloof to pressurise the Department of Public Works into selling it.
Ehrenreich, who is also the provincial leader of the ANC, said the land should be transferred to the Department of Human Settlements so that it could be used for low-cost housing development.
Dave Bryant, Tamboerskloof's DA ward councillor, said the land on which the army base was situated was worth a "considerable amount". But his primary concern was that the property had been allowed to fall into disrepair and the former base had become a "magnet for crime".
Ehrenreich said: "The city has done a land audit that [it is] not releasing as there would be public demand that the pockets of land in wealthier areas be used for low-cost housing. Instead, the city has now started a process of selling off the pockets of land in the wealthier areas to wealthy developers for upmarket housing."
Cape Town deputy mayor Ian Neilson said the city had a three-year land release programme. "As and when the city has determined which properties are surplus to the council's needs, we will release them to the market in a sustainable way," he said.