The revelation brings the total cost of cancelling the contract for the controversial project to at least $657 million.

The Treasury Corporation of Victoria, which manages the government's finances, has revealed in its annual report that it entered into an unusual deal with the Department of Treasury to guarantee against any losses associated with a massive $3 billion credit facility linked to the project.

Detail buried in the annual report reveals that, so far, the guarantee has cost the corporation $217 million, up from $191 million when the deal was initially locked in. The hidden blowout comes despite initial reassurances from the government that the cost of taking on the financial risks from the project would be negligible.

Treasurer Tim Pallas said he hoped the extra $217 million could be used in the future as a financial facility for other projects, claiming Victoria had dodged a bullet because of Labor's decision to dump the road project. He said the government had been transparent at all times, despite failing to initially disclose the extra liability.

"Go back an look at all the media releases ... we indicated that there were additional liabilities," Mr Pallas said.

The guarantee - known as an interest swap - does not expire until October 2021, and the ultimate impact on the budget bottom line remains unclear. But shadow treasurer Michael O'Brien, accused the government of lying about the true cost of cancelling the contract.

He said after factoring in money already spent, such as geotechnical work and land acquisition costs, the bill for the decision to dump the road was even more. He estimated the project has cost the state as much as $857 million.

"Daniel Andrews has been caught out lying again to Victorians about our state's financial position," Mr O'Brien said. "The decision by Daniel Andrews to scrap the East West Link contract and waste over $850 million will cost Victorians new schools, ambulance and police stations, trains and hospitals.  The tearing up of the East West Link contract has also cost Victoria up to 7000 new jobs at a time when our state is losing full-time jobs."

Labor announced in opposition that it would not build the road, arguing the contract signed by the former Napthine government just weeks before the November 2014 state election was not worth the paper it was written on.

But after the election it entered into a deal to pay the consortium $339 million to break the contract, with a further $81 million in fees to transfer a $3 billion credit facility for the project.