A plan to build a 12-mile bridge spanning Morecambe Bay between Cumbria and Lancashire has been unveiled.
A private consortium wants to construct the multi-million pound road and foot bridge between Barrow in Cumbria and Heysham in north Lancashire.
If approved the bridge would be one of the world's longest and create about 2,000 jobs.
But environmentalists have warned the project will have to meet tough guidelines as the bay is a Site of Special Scientific Interest and Special Protection Area.
A bridge spanning the bay could take up to an hour off road journey times between north Lancashire and the Lake District.
The initial plan outlines associated hydro-electric turbines to harness tide movements and a string of offshore wind turbines to generate enough energy to save 240 tonnes of carbon dioxide emissions daily.
Redshank are among the birds that visit Morecambe Bay
Plans have been submitted to Barrow Borough and Lancaster City councils.
A spokesman for the consortium, which includes British, Australian and Dutch investors, said: "There were plans to build a barrage 20 years ago, which was a disaster because it was concluded that it would destroy wildlife habitats across Morecambe Bay.
"We have decided to kick-start the process again. It's like throwing a pebble into Morecambe Bay and seeing where the ripples end up.
"The engineering for doing this is here and now. Twelve miles of causeway is easily achievable. It is the environmental conditions that are the key to this.
"The Government has given £1bn to promote wind power off Barrow, Morecambe and Heysham in the Irish Sea.
"We have the opportunity to make this a huge natural power platform which could become a showpiece for Britain."
He said the bridge would become a tourist attraction in its own right and could be a force for economic regeneration, creating 2,000 jobs.
Helen Johnston, marine conservation officer for English Nature, to BBC News Online: "Morecambe Bay has several elements which would need to be looked at, including its coastal lagoons, salt marshes and the various species living there.
"We would have an advisory role and would look closely at any impact assessments produced by the developers.
"Ultimately, if we thought the bridge would have an adverse impact on the bay, then we would have to consider asking for the plant to be called in for a public inquiry."