A £20 billion barrage across the Severn Estuary could be harmful to Bristol's economy, it has been claimed.

The Government is looking to harness the power of the estuary as it wants to produce 20 per cent of the UK's energy from renewable sources by 2020.

A 10-mile barrage from Brean Down, near Weston-super-Mare, to just south of Cardiff would generate more than 8.6 gigawatts, twice that of the UK's largest fossil fuel power plant and five per cent of the UK's energy needs.

But a forum of inquiry established by Liberal Democrat MPs, Welsh Assembly Members and councillors in the West of England and Wales has said it does not back the scheme.

Instead it supports another project, the Shoots Barrage near the Second Severn Crossing, which would be one seventh the width of the Cardiff to Weston proposal.

The recommendations came in a blueprint for harnessing the tidal power of the estuary, published by the Lib Dems yesterday.

The group argue there should be pilots of lagoon technology in the estuary, and that there should be "serious investment" in innovative technology.

This could include a tidal 'reef' or methods for storing tidal power so that it can be used at times of day when it is most needed.

The inquiry held evidence sessions in Bristol, Portishead and Cardiff, and has studied the documents which have been prepared by the Government as part of its own appraisal of options for Severn tidal power.

Government consultation on the schemes ends on April 23, after which it will publish responses and after consideration, announce its final shortlist.

The Lib Dem commission was jointly chaired by Northavon MP Steve Webb and Mike German AM.

Mr Webb said: "For over a century people have rightly been highlighting the potential for power generation from the Severn Estuary.

"With the threat of climate change getting steadily greater there is now real urgency that we get on with harnessing this source of renewable energy in an environmentally responsible way."

"We therefore reject the large 'Cardiff-Weston' barrage which could take decades to come on stream and could do untold damage both to the environment and to the local economy through its impact on the Port of Bristol.

"We believe that a smaller barrage offers the best mix of power output with reduced environmental impact and also offers the chance for a major upgrade to public transport through Wales and the West of England."

Environment Minister Mike O'Brien recently stated the latest construction figures for the Severn Barrage would cost between £19.6 billion and £22.2bn.

The four alternative options, including lagoons and two smaller barrages, cost a fraction of the barrage at a maximum of £6bn.