Tolls on the North East Link could be extended to other roads, according to tender documents released on Tuesday.

The Coalition and the Greens are warning that the government will toll the Eastern Freeway to fund the $15.8 billion ring road extension, according to the wording of the new documents, which indicates that the government is leaving the door open to road charges.

But Treasurer Tim Pallas has categorically ruled out tolling the Eastern Freeway to fund the North East Link, and accused the opposing parties of spreading lies.

The public document, which calls for advice on how motorists should be charged to drive on the North East Link, states that the state government needs the ability to toll other, additional roads.