The national police commissioner was given an ultimatum on Friday to attend to alleged corruption at the police forensic laboratory in Silverton, Pretoria.
"Failure to attend to these matters will leave us with no option but to mobilise all our resources for one of the biggest marches ever [under]taken by us," Gauteng Popcru secretary Matsemela Matsemela said.
He said national commissioner Riah Phiyega had seven days to act.
Police and Prisons Civil Rights Union (Popcru) was addressing the media on allegations that included sabotage to services, concealing or doctoring crime statistics, theft of drugs, irregular appointments, and sexual harassment.
Matsemela said Phiyega and Parliament's police portfolio committee were informed of the allegations on June 25, but had failed to act.
"Given the sensitivity of that institution and the nature of the allegations... after you received such allegations you ought to have acted," he said.
"Something is absolutely wrong there... They have the proof but they don't want to act."
Matsemela said the union had handed Phiyega a file of evidence on all their allegations and she had not responded. The union claimed its members who informed them of the allegations had been victimised through disciplinary hearings.
"These disciplinary hearings are formulated with the sole intention of creating (casting) doubt on the credibility of information provided by these members and also serve as a basis to hide corruption."
In April, the head of the laboratory made a presentation to the portfolio committee, in which he said there was a backlog of 182 cases. Matsemela however said the backlog was actually at 5000, after all the cases were consolidated.
Matsemela said between 2008 and 2010, drugs with a street value of R500 million were stolen from the laboratory.
Popcru wanted Phiyega to appoint a commission to investigate all the allegations, suspend the head of the division pending the outcome of the investigation, and provide whistle-blowers with protection.
"We expect nothing whatsoever from her, but to act on these serious corrupt activities," he said.
At a meeting in August Phiyega called on Popcru to declare "war on corruption and criminality" within the police.
By 5.30pm on Friday afternoon, Phiyega's office could not be reached for comment.