( BBC ) - An influential UK government advisory body has endorsed proposals for a tidal barrage across the Severn estuary.
The Sustainable Development Commission (SDC) says the project should meet "tough" environmental conditions and remain in public ownership.
Last week the government announced an inquiry into the Severn scheme, which is opposed by a number of green groups.
The SDC, chaired by Jonathon Porritt, says the UK could get at least 10% of its electricity from tidal power.
Its report, Turning the Tide, was launched at parallel events in London and Cardiff.
"We are excited about the contributions a Severn Barrage could make to a more sustainable future, but not at any cost," Mr Porritt said.
"The enormous potential... 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."
The SDC outlined a number of conditions that would have to be met in order for the massive project to win the commission's support.
Firstly, the barrage had to be "publicly led as a project and publicly owned as an asset" to ensure that the government was responsible for the long-term sustainability of the project.
The report said that the lower rates of interest available to a government-led project would provide consumers with competitively priced electricity.
It also called for a large-scale "compensatory habitat" package to replace breeding and feeding sites for migratory birds around the estuary that would be lost if the barrage got the go-ahead.
The commission also said that it would only support the 16km-long structure if it was constructed within the parameters of existing European environmental legislation, such as the EU Habitats Directive.