The seafront line opened in 1865 to provide a link from the railway station to the quay and Channel Island ferries.
The last regular service ran in 1987 but the line was used for special occasions until 1999.
Andy Spreadbury believes re-launching the line would also help with parking problems in the town during the summer.
The tracks to the quayside remain in place, making the route still viable, said Mr Spreadbury, who worked on it in the late 1970s.
Network Rail said while the main line to Weymouth is electrified, the seaside track is not, which could make a reopening of it problematic.
He added: "It's unique, it's the last one of its kind in the country, at this gauge anyway.
"It can be a major tourist attraction because it's so unique.
"We're not yet looking at costs. We are just putting it out to consultation to see what people in Weymouth think."
There have been previous attempts to reopen the line but Weymouth and Portland Council said none had been financially viable.
It had voted to acquire the track from Network Rail in a Â£50,000 deal in 2009 but the sale never went through, a spokesman said.
A Network Rail spokesman said: "If the council decided they wanted to do something with it we are happy to do that, whether its keeping it as a railway, cycle track or tramway.
"But if the local authority, community or an operator said they wanted to see trains back, we would work with them to achieve that but it would depend on a solid business case."
The most recent attempt to reopen the line was made by enthusiasts who wanted it used to bring spectators to the sailing events during the 2012 Olympic Games.
A former Dorset seaside train line worker has launched a campaign to return the service through Weymouth in a bid to boost tourism.