Cosatu threatened mass action on Thursday against e-tolling in Gauteng after the Constitutional Court overturned an interdict to halt the project.
"We are going to resist it with every power we have," Congress of SA Trade Unions (Cosatu) general secretary Zwelinzima Vavi told reporters on the sidelines of Cosatu's 11th national congress in Midrand.
"Cosatu remains absolutely determined to oppose the tolls at the street level. The mobilisation... is not over.
"The call we want to make to workers and all of the people who supported us in opposition to the e-tolls is not to drop your guards. We need your energy and your unity more than [at] any other time before," he said.
Vavi said Cosatu was not surprised by the court's decision.
"Our objection to the introduction of e-tolls in Gauteng was never based on whether they are legal or not," he said.
"It was a political decision to oppose what we regarded as a move to privatise the roads and to use the user-pay principle on the poor in a manner that sidelines them and forces them onto the potholed roads that are used by the municipalities."
He said the government needed to wait for talks between concerned parties and Deputy President Kgalema Motlanthe to find "alternative means" to pay back debt incurred in the construction of the roads, before implementing the tolls.
"In our view, it would be a huge mistake by government if it was to steam ahead on the basis of the Constitutional Court judgment and implement what we all know is an extremely unpopular policy decision," Vavi said.
"There will be no e-tolling. The programme of action that we will be announcing this afternoon [at the congress] includes the fact that we will oppose the tolling of the roads in Gauteng."
He said the tolling could possibly be implemented in other provinces.
"This is the first step, this will go everywhere if the government succeeds to ram it down the throats of the people of Gauteng."
The Constitutional Court set aside an interim order that put Gauteng's e-tolls on hold on Thursday.
"The interim order granted by the high court of 28 April, 2012, is set aside," said Deputy Chief Justice Dikgang Moseneke.
This was because the high court had not considered the separation of powers between the court and the executive.
The High Court in Pretoria granted the Opposition to Urban Tolling Alliance (Outa) an interdict on April 28, ruling that a full review needed to be carried out before electronic tolling of Gauteng's highways could be put into effect.
The interdict prevented the SA National Roads Agency Limited (Sanral) from levying or collecting e-tolls pending the outcome of the review.
Sanral and National Treasury appealed the court order, and said delays prevented the payment of debts incurred building gantries.
Reading the unanimous judgment, Moseneke said the separation of powers was vital to South Africa's constitutional democracy.