The Commission's report, Tidal Power in the UK, draws on extensive research and public and stakeholder engagement to reach the conclusion that, the UK's outstanding tidal resources could provide at least 10% of the country's electricity through a combination of technologies. A Severn barrage alone could potentially supply just under 5%

However, the report insists that commitment to public leadership and ownership of the project is the only way to ensure the public gets a fair share of the rewards and to avoid short term decisions. It also asserts that a publicly led project is the only way of ensuring that the network of estuary habitats protected by European law is not compromised as a result of a Severn barrage.

The concept to build a £14bn tidal barrage across the Severn from south of Cardiff to southwest of Bristol could harness power from both inbound and outbound tides in a location which has the world's second largest tidal range.

Jonathon Porritt, chair of the Sustainable Development Commission said, 'The enormous potential for a Severn barrage to help reduce our carbon emissions and improve energy security needs to be balanced against the impact on the estuary's unique habitat, as well as its communities and businesses. This is why we believe that any development must be publicly led as a project and publicly owned as an asset, in order to ensure that the Government takes full responsibility for taking a sustainable, long-term approach.'

The report also highlights the fact that the lower rate of interest available to a Government led project would provide the only realistic way of financing a large scale compensatory habitat package, as well as providing electricity to consumers at a competitive price.

The Commission also warns that the development of major tidal power resources should not be seen as a licence to ignore the need for dramatic reductions in our energy consumption, increased energy efficiency, and the wider decarbonisation of our energy supplies.

A barrage would be only one part of a major long term sustainable energy strategy for reducing carbon emissions. Reviewing the different types of tidal technology, the report asserts that the way is open for the UK to exploit some or all of its rich tidal resources for tidal barrages, tidal lagoons or tidal stream devices.

Emerging tidal stream technologies present opportunities for low carbon energy production, and the report cites potentially huge rewards in terms of export potential from developing this technology. The Commission concludes that Government should 'stay the course' to make tidal stream technology a viable proposition, whilst putting in place a robust regulatory framework and supporting the research required to understand potential environmental impacts.

The report concludes that there are few direct conflicts between tidal barrages and tidal lagoons, with the exception of claims made for large scale lagoon development in the Severn Estuary. Although there is little authoritative evidence available on tidal lagoon technology, which proposes using hydropower turbines in an offshore impoundment, lagoons could potentially be developed in a number of shallow coastal areas with sufficient tidal range. The Commission would like to see the Government investigating their long term potential by funding a demonstration project. This would allow a full evaluation of the costs and the potential environmental impacts.

Tidal Power in the UK was funded by the Department of Business, Enterprise and Regulatory Reform (BERR), the Welsh Assembly Government (WAG), the South West of England Regional Development Agency (SWRDA), the Scottish Government, and the Department of Enterprise, Trade and Investment (Northern Ireland).