Congress of SA Trade Unions Western Cape general secretary Tony Ehrenreich told reports on Sunday afternoon that a planned march on parliament across the city centre would likely attract 30,000 people on the day.
"It will be one of the biggest strikes that has happened in the Western Cape for a long, long time," he said during a media briefing at his organisation's Salt River headquarters.
The march is set to start at 10.30am on Wednesday and will proceed from Kaizergracht to the gates of parliament where a memorandum will be handed over to the minister of labour.
"We think we'll have about 30,000 people," he said.
About 20,000 of these would be Cosatu members. A further 10,000 from civil society organisations and unions would also join in.
The Cape Town march is part a nationwide series of protests against, among other things, the controversial practice of labour broking and government's decision to push ahead with plans to levy e-tolls on Gauteng's freeways.
Ehrenreich said permission for the march to go ahead had been obtained from the City of Cape Town and arrangements made with the local traffic department as well as the SA Police Service.
Present at Sunday's briefing were several civil society and non-governmental organisations as well as representatives from unions in the textile, nursing, education, mining and commercial sectors.
Responding to a question on whether teachers would be joining the march, Ehrenreich said:
"There won't be a lot of education happening on the day of the strike."
He said Cosatu had drafted in extra marshals to help control the march, which would be "disciplined" and "safe."
Cosatu Western Cape chairman Dan Melapi said the union federation and its partners were determined to put an end to labour broking.
"[it is] a practice which is nothing less than a form of human trafficking, reducing workers to commodities, hired out to companies like sacks of potatoes, usually with no benefits, poverty wages and no job security."
On e-tolling Molapi said roads were national assets, "not a commodity which can be used to make profits at our great expense".
Ehrenreich said the strike "born out of frustration."
He said the concession government had made on e-tolling including capping the maximum toll rate and reducing the price did not go far enough.
"A few companies are milking the public purse," he said.