Johannesburg - Cosatu wrote to the transport department on Wednesday, reiterating its call for the scrapping of e-tolls.
Road maintenance funds should be taken from tax revenues, not from motorists, Congress of SA Trade Unions spokesperson Patrick Craven said.
Tolls would have a large impact on the poor, their transportation methods and food prices, while specific private companies would benefit in the long run.
"This will not just affect the people of Gauteng, as the government has now conceded that e-tolling will replace the existing toll-gates throughout the country."
Craven said South Africans were already deep in debt and the tolls would just add to their woes.
"The point is that large numbers of private vehicle users simply do not have a single extra rand to spend. The logic of the 'user-pays' principle is that those without the money to pay the tolls should be excluded from access to the best roads."
After months of debate, the proposed toll prices were reviewed and lowered in October. The SA National Roads Agency Limited said e-tolling would cost motorists with e-tags 30c/km. This was a reduction from the 40c/km decided on last year.
The e-tag tariff for motorcycles had also been dropped from 24c/km to 18c/km, for medium heavy vehicles (Class B) from R1/km to 75c/km, and heavy vehicles (Class C) from R2/km to R1.50/km.
The system was scheduled to start operating on November 26.