The Conservatives have announced a "priority" review of the Oxford to Cambridge expressway if they win the general election.
Transport Secretary Grant Shapps said the party will "look at alternative plans" to the Oxford to Milton Keynes and M1 section of the scheme.
Campaigners against the link road have called on all parties to stop the scheme over concerns about housing.
Mr Shapps said the scheme will only "proceed" if it has "local support".
The project aims to provide a "fast, high-quality road link to better connect Oxford, Milton Keynes and Cambridge", Highways England said.
The No Expressway Group's main concern is the "inappropriate housing targets" it says are included in the plans.
The group also said the new government should "shift investment from private, car-dependent transport to public transport systems".
A representative for the Liberal Democrats said a review would be "pointless". The Labour Party has been contacted for comment.
Chair of the No Expressway Group Olivia Field said: "The scale of development from the proposed expressway and aspiration for one million new homes along the Ox-Cam Arc would be devastating for our environment, our health and our communities for generations to come."
Mr Shapps said the "benefits" of the project were "finely balanced against its costs, both financial and environmental".
"If re-elected we will review as a priority this scheme to ensure that it is still worth going ahead," he said.
"We will not allow the scheme to proceed if there is not a strong case that it will boost jobs, prosperity and has local support."
Layla Moran, the Liberal Democrat candidate for Oxford West and Abingdon, said the announcement by the Tories shows the party is "finally aware of how unpopular their expressway plans are" with the local community.
"We don't need a pointless government review," she said.
"We need an urgent public consultation to give residents the opportunity to not go ahead with this disastrous motorway altogether, as I and the Liberal Democrats have been saying since day one."
Other candidates standing in Oxford West and Abingdon are: James Fredrickson (Con), Rosie Sourbut (Lab) and Allison Wild (Brexit).