Opposition to Sydney's $16.8 billion WestConnex motorway project is gathering pace after Marrickville Council used its powers to try to block contractors from accessing roads to carry out preliminary work.

In a further sign of the level of resentment in the city's inner west to the project, the council has refused to grant WestConnex a road operating permit to install underground electricity mains to service the proposed spaghetti junction of motorway ramps at St Peters.

The council, which has been a vocal opponent of the new motorway, rejected the permit to work on eight roads on the grounds that government approval has yet to be given for the second stage of the project.

It is has told WestConnex and subcontractors that it will not consider other applications to carry out work until the project is approved.