Backers of plans for a tidal energy "barrage" across Britain's River Severn estuary will meet with British Prime Minister David Cameron, its chief supporter says.

Welsh Member of Parliament Peter Hain told the Western Mail newspaper that Cameron has agreed to have a meeting him on the project -- a privately funded plan to construct an 11-mile-long concrete barrier stretching across the estuary from Cardiff, Wales, on the north to Weston-super-Mare, England, on the south.

The $47 billion idea, being floated by Corlan Hafren Ltd., aims to tap the immense tidal energy potential in the river estuary, which sees daily tidal ranges of 23 feet to 46 feet during spring tides.

After earlier Severn estuary proposals were rejected by Westminster as too costly to be feasible, the Corlan Hafren consortium's has become the first to merit the personal attention of a British prime minister, Hain said.

"During Prime Minister's Questions (May 16) I asked for a meeting with Mr. Cameron over the project," Hain told the newspaper. "He has since agreed and we are now fixing up a meeting, which could be next month, where I will take the consortium to see him."

Hain, an MP from Neath, Wales, last week resigned as Labor Party's shadow secretary for Wales partly to concentrate on the Severn barrage project.

He and other backers say it could generate as much as 5 percent of Britain's energy needs at a time when an expansion of nuclear power is in doubt. The Corlan Hafren proposal would feature more than 1,000 "state-of-the-art" turbines embedded in the concrete barrage and would use both ebb and flow tides to generate power.

The project will have the "biggest, most positive effect on Wales of anything in the next few years, short of government macro-economic policy," Hain told the newspaper.

"There will be tens of thousands of jobs created in the construction industry and potentially tens of thousands more in other sectors," he said.

Among its hoped-for spinoff benefits would be new road and rail transportation routes linking South Wales and southwestern England, creating a cohesive market of 2.2 million people living in and around Cardiff and Newport in Wales and Bristol in England.

Schemes to tap tidal flow in the estuary have been around for 20 years but none have been built due to the cost. A $54 billion publicly funded proposal was studied by the British Department of Energy and Climate Change for eight years but rejected as not worth the investment.

There are substantial environmental concerns for bird and fish populations of the estuary, as well as over its status as a surfer's haven and whether a massive concrete barrage spanning the channel is the best way to capture its tidal power.

"Looking at the range of renewable energy options available to U.K., the barrage seems to be a poor choice," Greenpeace Chief Scientist and Policy Director Douglas Parr told The Guardian.

"Previous feasibility studies have shown it is expensive, damaging to globally significant habitat and not scalable -- in other words, once you've done a barrage in the Severn, that's a lot of the resource used, whereas wind/solar/geothermal/tidal stream can be replicated in many places."