Ministers will next week pronounce the Severn barrage plan is dead as they announce no state subsidy is available for the world's largest energy project, the Western Morning News understands.

On Monday, Energy Secretary Chris Huhne is expected to make public a long-awaited study into the feasibility of energy generation across the Severn estuary between Somerset and south Wales. He is likely to rule out public funding for the controversial £20 billion plan, claiming that research and development cash can be better spent on energy projects elsewhere.

After decades of attempts, it will mark the end of the latest attempt by a British government to harness the energy of one of the world's largest tidal ranges – the difference between the high and low tides.

The announcement will please some environmentalists, who were worried about the impact on bird and marine life in the estuary.

But others say the move undermines David Cameron's pledge to be the "greenest government ever".

Without public backing to underpin the costs, the private sector is unlikely to back the ten-mile tidal barrage, which would be able to provide 5 per cent of the UK's electricity.

There have been suggestions that ministers will examine one of the smaller, embryonic projects to generate energy on the Severn, but they will give no guarantee that it will go ahead.

It is understood that Mr Huhne favours investing in technology to capture carbon dioxide emissions from power stations and industrial sites, an area where Britain stands to be a world leader.

There is also no guarantee the technology would be effective, risking massive overspends.