The government has been accused of failing to spend any of the £42m budget set aside for the development of wave and tidal energy technologies.
The Liberal Democrats said they had obtained figures showing that the entire budget for the Wave and Tidal-stream Enegy Demonstration Scheme is unspent, four years after it was announced.
The party also claimed that a £2m budget for monitoring the environmental impacts of wave and tidal projects is also unspent.
Jo Swinson, who obtained the information through parliamentary questions, said: "These figures show the yawning gulf between rhetoric and reality when it comes to this government's record on renewable energy.
"Britain has world-leading potential when it comes to wave and tidal energy, yet the government is sitting idly on the funding which the sector so desperately needs.
"How can the government hope to meet its targets on renewable energy when it is not even capable of spending the modest funding it has set aside for wave and tidal technology?
"This is a vital time for the development of the renewable energy industry. Instead of spending so much time pushing its nuclear energy agenda, the government should be focusing on getting funding for renewable technologies to where it's needed."
A department for business, enterprise and regulatory reform spokesman said: "The government has not squandered this money.
"The £42m has been set aside to help an industry in its infancy and we have a duty to make sure public money is spent in the most effective way.
"We have already made in excess of £100m available to the wave and tidal industry which has helped to take projects from the drawing board and into the water.
"We are now taking a more flexible approach with the entry criteria of the £42m Marine Renewables Deployment Fund which will help speed up applications and help ensure the UK remains at the forefront of the development of this new technology."
Dods Parliamentary Communications Ltd