The Gauteng branch of Cosatu on Friday said government should look at enforcing a once-off tax on everyone who earns over R600 000 a year.
The federation said this money could then be used to pay for the province's toll roads.
In April, Judge Bill Prinsloo granted an urgent interdict effectively putting the controversial project on hold. His decision was handed down in Pretoria's North Gauteng High Court.
Gauteng Cosatu spokesperson Dumisani Dakile said private companies should also be made to pay up.
He said corporations should pay at least one day's profit towards the project.
On Thursday, Cabinet said it would consider e-toll alternatives to fund and maintain Gauteng's freeways.
The Opposition to Urban Tolling Alliance (Outa) had called for a fuel levy to fund the Gauteng Freeway Improvement Project.
Government approached the Constitutional Court in Johannesburg to appeal against April's ruling. Under the project, motorists are expected to fork out at least 30 cents per kilometre to use a large stretch of the province's highways.