The Victorian government continues to blame Transurban and builders of the troubled $6.7 billion West Gate Tunnel project for problems and delays, despite its own environmental agency botching the approvals to move toxic soil.

Troubles for the problem project escalated further on Thursday, after the state's Environment Protection Authority rescinded the approvals to accept contaminated soil, described by the state opposition as a "monumental stuff-up" and with builders claiming the ball is in the state government's court.