Gauteng road users have been urged not to buy e-tags after the High Court in Pretoria on Thursday dismissed an application to scrap e-tolls.
"Don't register! Don't buy e-tags!" the Congress of SA Trade Unions said in a statement.
Spokesperson Patrick Craven expressed disappointed at the judgment and said Cosatu would approach Parliament and continue its mass action.
He said tolls would add to the burden on the poor and affect motorists in other provinces once the transport department rolled tolling out across the country.
"Tolls will also put an indirect burden on the poor of the whole of South Africa, by adding to the cost of transporting goods, and will have an immediate effect on food inflation."
Craven said the system would see a large portion of the revenue going into the pockets of toll operators.
On Thursday, Judge Louis Vorster found the Gauteng Freeway Improvement Project (GFIP) was lawful and dismissed an application by the Opposition to Urban Tolling Alliance (Outa) to have e-tolls on Gauteng's highways set aside. He said the application could not succeed and ordered Outa to pay costs.
Anti-toll activist Rob Handfield-Jones said the consultation done in 2012 proved the public had very little understanding of the implication of e-tolls in 2007.
"Sanral's version of 'consultation' was akin to getting someone to agree to a dam being built nearby without telling them their house would be flooded when the dam was filled," he said.
"Using Sanral's figures, GFIP has cost R113-million per kilometre to build. How is this possible for what amounted mostly to large-scale re-surfacing?"
Handfield-Jones called on road users to reject the "unjust and uneconomical system" and to not buy e-tags.
"Do not pay toll fees. The system relies on voluntary compliance... It will be impossible to prosecute tens of millions of offences per month."
The Justice Project SA (JPSA) expressed concern at the decision to order Outa to pay the legal costs for Sanral, the transport department, Treasury, the Gauteng roads and transport MEC, minister of water and environmental affairs and the department's director general.
"Given the fact that government has spent [an] estimated... R30-million of taxpayers' money on defending this matter, should Outa have to pay government's legal expenses, there is no doubt that Outa will not be able to do so," chairman Howard Dembovsky said in a statement.
"This will expose the directors of Outa to be held responsible in their personal capacities. This will send a very clear message to non-governmental organisations not to take government on in court, regardless of how good their case may be, just in case they lose."
The judgment sent the message "don't screw with government or you will be bankrupted".
Freedom Front Plus spokesperson Anton Alberts said the campaign against e-tolling would continue.
Outa's chairman Wayne Duvenhage said they were still not sure whether to appeal or take the matter to a higher court.
Transport director general George Mahlalela said it was unclear when the minister would make the implementation announcement, but that it would not happen in 2012.
"There will still be people who are unhappy with the outcome and there is nothing we can say. If people opt for civil disobedience we hope they will not do illegal things."
Earlier, the government and Sanral welcomed the decision and urged motorists to buy e-tags.