Liberal Leader Brian Gallant says he would press the federal government to complete the restoration of the Petitcodiac River if his party is elected in September.
"We want to return the Petitcodiac to its full and former glory,” he said on Thursday.
"The health of the Petitcodiac River has improved dramatically since the causeway's gates were opened four years ago, but more work remains to be done."
Gallant wants to replace up to 280 metres of the causeway with a bridge, which would allow for the river to be widened, restoring its full tidal flow.
The plan was first proposed by the Liberals in 2007 at a cost of $68 million.
"There are also economic reasons for completing the restoration," said Gallant. "The tourism and recreation benefits alone could generate millions for the city and region economy as we saw last summer."
Federal MP Robert Goguen has previously said widening the river from 100 to 146 meters is not a priority for local politicians.
He has suggested upgrading the sewage plant might be a wiser use of federal money.