The public is not fooled by the reduced e-toll tariffs, the Opposition to Urban Tolling Alliance (Outa) said on Tuesday.
"They [the public] know the rate of today is not the rate of tomorrow," Outa chairperson Wayne Duvenage said in a statement.
He Business Day reported on Monday that further cuts to tariffs were under consideration.
According to the newspaper, Transport Minister Ben Martins said in an interview last week his department was "working very hard" to find ways to soften the effect of e-tolling.
Duvenage questioned the timing of the possible tariff reductions.
"Have the collection costs suddenly been reduced, or is this a case of trying to force a thinner edge of the wedge into the door of public acceptance?" he asked.
"Sugar-coating the pill now merely prolongs that pain that society will have to endure later, unless of course there will be more transfers from Treasury under renegotiation of the contracts to significantly reduce the costs of collection."
He said the government was not noticing how people in countries like Egypt, Brazil and Turkey were standing up against governments which took their citizens for granted.
"Our government seems not to notice these developments and the possibility of similar incidents unfolding in South Africa," he said.
"Such protests will be detrimental to investor confidence and our fragile economy, yet they simply continue to ignore their people on this important issue and other matters."
On May 24, draft regulations and notices were published in the Government Gazette detailing how the tolls would work.
The regulations proposed a reduction of the R550 a month cap for cars to R450.