NO SOUTH African worker can be dismissed for taking part in Wednesday's nationwide protest against the e-tolling system and labour brokers, the Congress of South African Trade Unions (Cosatu) said on Monday.

"The strike is protected ... and we have complied with the legal requirements," Dumisani Dakile, Gauteng secretary of the federation, told reporters in Johannesburg. "Not a single worker can be threatened with dismissal."

Mr Dakile said the strike certificate issued by the National Economic Development and Labour Council covered every South African worker, whether or not they were members of Cosatu.

"We are even calling on employers to join the march and not threaten workers," he said.

Cosatu expects at least 100000 people to take part in various marches on Wednesday. The main event will take place in Johannesburg's central business district.

Tolling of 185km of the N1, N3, N12 and R21 freeways around Johannesburg and Tshwane is expected to start on April 30. Motorcycles with e-tags will pay 20c/km and those without will pay 38c/km. Light motor vehicles will pay 30c/km and 58c/km, respectively, and non-articulated trucks 75c/km and R1,45/km.

Articulated trucks with e-tags will pay R1,51/km and those without R2,90/km.

Under the new fee system, the cost for motorcycles and light vehicles will be capped at R550 a month.

Cosatu, which wants the system scrapped, said it expected its provincial bodies, essential services workers, Eskom workers, teachers, pupils and other unions would join the strike.

Minimum essential service levels would be ensured, said Mr Dakile. "Those departments won't be left unmanned," he said.

Protesters will start gathering from 8.30am in Johannesburg on Wednesday and the march will start at 10am.

A memorandum will be handed to the Department of Labour in Randfontein. Marchers will then proceed to downtown Johannesburg to hand a memorandum to the premier's office and to the Transport Department.

Mr Dakile said the march would be peaceful and monitored by 10000 marshals.

Cosatu has said that labour broking is worse than apartheid. "Apartheid was much better. The slave system was much better than labour brokers. It's human trafficking, one human selling another human."

If there is no positive outcome from Wednesday's protest, a second march will be planned.

The Federation of Unions of South Africa has advised its members not to take part in the strike, saying it might render some members unprotected and expose them to possible disciplinary action.