Plans for a six-mile sea wall in Swansea Bay have been panned by the Citizens Advice charity.
The consumer body called it “appalling value for money” which should not get subsidies.
The green energy scheme would harness the power of the tide to provide green energy for 100,000 homes.
The £1bn project would see the wall formed as a causeway for pedestrian use but would enclose 16 huge underwater turbines to generate power.
But Citizens Advice has said that it would “squander” billpayers’ cash, and make them pay more money for electricity than from any other major UK green project to date.
Tidal Lagoon Power, the company behind the project, said it should deliver an almost £200m boost to the UK engineering sector with Tidal Lagoon aiming to ensure that 65% of capital expenditure on the project is in Britain.
The tidal power scheme has been designated a nationally significant infrastructure development under the Planning Act and is currently going through the planning process to gain consent, with the intention of it being up and running by 2019.
If built, the tidal lagoon would be “per unit of output, the most expensive significant renewable energy project in Britain”, Citizens Advice said.
It urged ministers to allocate the finite green energy subsidies to the most cost-effective projects.
