Labour said it would go ahead with improvements to the A27 if elected, with the exception of the Arundel bypass.
This week Liberal Democrats and Conservatives attacked the party for saying it would delay the £350m plan to tackle congestion on the major route.
But Labour went on to dispute this, saying it wanted the A27 scheme to be carried out, but without the Arundel bypass.
A spokesperson for Labour said: “Labour is today saying that we intend to go ahead with the agreed works on the A27 with the exception of the specific Arundel bypass – this is due to cut through a National Park and so raises a number of environmental issues that need be resolved before we give this one section of road improvement the go ahead.
“Instead of an uncosted Tory plan they have no idea how they will pay for, Labour will deliver a fully funded rail fares freeze.”
Lloyd Russell-Moyle (Lewes Constituency Labour Party candidate) added: “We’ve heard promises on improving links between Lewes and Eastbourne before, but with little action. We will keep rail fares down whilst improving the safety of the A27.”
The successful funding bid to improve the route across East and West Sussex was announced by the coalition Government shortly before Christmas.
Proposals include a new bypass at Arundel, improvements at Worthing and Lancing, upgrades to the junctions at Chichester, and money for the Lewes to Polegate stretch.
Labour’s General Election manifesto, unveiled on Monday April 13, was understood to commit to a one-year freeze on rail fares paid for by delaying major road projects in the South.
Former Lib Dem MP for Lewes, Norman Baker said: “I have long campaigned for essential safety improvements along this road and continue to do so. That is why I welcome the £75m allocated by the Treasury for the Lewes-Polegate section which will fund further safety improvements but without the highly destructive and hugely expensive scheme proposed by Tories from outside the constituency, which would wreck our lovely countryside and damage our villages.
“Whatever the position in West Sussex, which is outside my patch, it is totally irresponsible of Labour to say they will pull the plug on works between Lewes and Polegate that are supported by all the local parish councils and me, and which will save lives, as well as helping those on foot and on bike.”