Building a bypass around Nowra is inevitable, according to Kiama MP Gareth Ward.
But Mr Ward said that shouldn't rule out building the third Shoalhaven River crossing now.
"A Nowra bypass will have to happen one day, there's no doubt about that," Mr Ward said, "but we could not reduce the people of Nowra and Bomaderry to just one bridge."
Mr Ward said the existing southbound bridge was more than 100 years old and was "fast reaching the end of its serviceable life" in terms of vehicle crossings.
Putting off building the new bridge risked the possibility of the old bridge closing due to age and residents being left with just one river crossing.
"Could you imagine if we couldn't service the old Nowra bridge any longer and we had to close it?".
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"As a result we would have to use the newer of the two bridges to service both directions. Can you imagine, with today's traffic volumes, what would happen to congestion?"
Despite the likely high cost of a Nowra bypass - which could require another bridge - Mr Ward said there was no escaping the fact there would come a time when it was needed.
"A Nowra bypass would be north of $1 billion in terms of the cost," he said.
"We need to do that one day but what is most pressing at the moment is making sure there is security of crossing of the Shoalhaven River."
The need for a Nowra bypass was raised quite a lot in the community feedback to plans for the new bridge.
The report on feedback released last year found it was not a better option than a new bridge as it would only take around 15 per cent of current traffic off the highway at the Shoalhaven River.