Labor has promised to spend $600 million to build dual carriageway from Nelson Bay to Fern Bay if it wins and retains government over the next eight years.
Shadow Minister for Roads, Maritime and Freight Jodi McKay and Port Stephens MP Kate Washington made the announcement on Tuesday beside Nelson Bay Road at Salt Ash, across the road from where Premier Gladys Berejiklian and Port Stephens Liberal candidate Jaimie Abbott pledged $275 million in January.
In dollars and scope, the Labor project trumps the Liberal promise to duplicate the road from Williamtown to Bobs Farm in three years.
Labor pledged on Tuesday to spend $275 million on the road in a first term of government, the same as their opponents, and another $325 million between 2023 and 2027 if elected again.
The Liberals announced $188 million for a Fingal Bay link road last week.
The two major parties have now promised more than $1.5 billion for roads in Port Stephens and the Upper Hunter, the only two marginal seats in the region leading into the March 23 election.
The only Hunter road promise outside the two marginal electorates has been Labor's pledge to fund the $32 million Pennant Street bridge linking Glendale and Cardiff.
Ms Berejiklian also committed $780 million on Sunday to redevelop John Hunter Hospital, a pledge Labor quickly promised to match.
The Labor MPs said full duplication of Nelson Bay Road would be completed in three stages, from Medowie Road to Stockton, Williamtown to Bobs Farm, and Anna Bay to Nelson Bay.
Ms Washington said a Labor government would consult with Roads and Maritime Services before deciding which section it would complete first.
Former Liberal premier Mike Baird promised $70 million to fully duplicate the road just before the 2015 election, but little of that money has been spent. That funding was bundled into the $275 million Ms Berejiklian and Ms Abbott committed in January.
Ms McKay and Ms Washington sought to differentiate Labor's "practical, reasonable and deliverable" promise from the "sour taste" left by the government's record on funding the duplication.
"This commitment is dependent on two terms of a Labor government," Ms Washington said.
"We're not going to stand here like the premier did and say we're going to do the next stage in two years … and then she called that an ambitious plan. I just want people to start having some faith in the process again."
Ms McKay challenged Ms Berejiklian to match Labor's commitment to duplicate all of the road.