National Grid has been forced to defend payouts of £180m to a string of reserve power plants which were never called on over the three years of the scheme.

It set up the reserve system over fears that the steady shutdown of old power plants would put the UK at risk of potential blackouts.

However, the Energy and Climate Intelligence Unit think tank said the fears were overblown, and had lead to “excessive spending” to create an insurance policy against a risk which had not materialised.

James Heappey, a former member of the Commons energy select committee and an advisory board member of the think tank, said the report shows that National Grid’s £180m spend was “completely unnecessary”.