Ecotricity boss Dale Vince questions Swansea tidal lagoon
A leading renewable energy firm has written to the UK Energy Secretary Greg Clark attacking plans for a £1.3bn Swansea Bay tidal lagoon.
Ecotricity believes tidal energy would be cheaper to produce completely offshore.
It said it was also important to be "business-like" and open up the process to other companies from the first stage.
The UK government said it was still assessing plans for the Swansea scheme.
Tidal Lagoon Power, which has put forward the plans, said it welcomed other developers looking at their own plans.
Ecotricity's owner Dale Vince told BBC Wales economics correspondent Sarah Dickins that the cost of the Swansea project should be borne by tax-payers not bill-payers.