Gauteng highways are national assets and not commodities for profit, Cosatu secretary general Zwelinzima Vavi said on Thursday.
"These roads are national assets, for the use of the people of South Africa, not a commodity which can be used to make profits at our great expense," he told reporters in Johannesburg.
"The federation will continue to campaign for an efficient, safe, and affordable system of public transport."
Tolling is imminent on 185km of the N1, N3, N12 and R21 around Johannesburg and Tshwane.
With effect from April 30, motorcycles with e-tags will pay 20 cents a kilometre and those without, 38 cents.
Light motor vehicles will pay 30 cents and 58 cents respectively, and non-articulated trucks 75 cents and R1.45.
Articulated trucks with e-tags will pay R1.51 a kilometre and those without R2.90.
Under the new fee system, the cost for motorcycles and light vehicles will be capped at R550 a month.
Vavi said Congress of SA Trade Union (Cosatu) affiliates and provincial structures reported overwhelming support for a March 7 strike against e-tolling and for banning labour brokers.
"It's all-systems go for the biggest mass protest in years," he said.
"We call on every South African to join this protest action be they black or white, rich or poor."
Cosatu said it would not participate in a court application to halt e-tolling.
"We are not part of it mainly because of the Democratic Alliance's participation in it," said Vavi.
"We wish them well. We won't join it. We will play our role outside.
If they win, we will also benefit, of course."