Kemi Badenoch has suggested that net zero targets “with no plan will bankrupt Britain”. The Tory leader suggested Labour would “never” be able to deliver on its pledge to cut bills by £300 after the Government increased the maximum electricity price it is prepared to guarantee companies developing new wind farms.

The maximum guaranteed price on offer for offshore wind farm developers will be £113 per megawatt-hour, up from £102/MWh last year. For onshore wind, the maximum price has climbed from £89 to £92/MWh. All prices are at 2024 levels.

Mrs Badenoch said: “This is why I warned that net zero targets with no plan will bankrupt Britain. Keir, Rachel and Ed promised to cut bills by £300. It was always clear they could never deliver on that pledge, and now businesses and families will pay the price of these ludicrous contracts.”

On Wednesday, ministers published the terms for this year’s upcoming auction of subsidy contracts for renewable energy projects that will be built over the next several years. It wants it to be the largest auction yet in order to meet its clean energy goals.

The Energy Secretary has vowed to almost completely rid Britain’s electricity grid of fossil fuels by 2030, a goal he defines as using renewable energy 95% of the time.

This is five years sooner than the previous commitment made under the previous Tory government.

Shadow Energy Secretary Claire Coutinho said there was “no way” Labour could bring down bills with its wind auction prices.

She said: “These are eye-watering prices – the highest in a decade and way above the average cost of electricity last year. And this is before the hidden costs of grid, storage and wasted wind, which all end up on our energy bills.

“As I’ve been warning, Ed Miliband can’t cut bills by £300 like he promised because he will always put his net zero zealotry above the economy or the cost of living. Cheap energy must come first.”

The increases come despite the Government extending the length of the contracts up for auction, from 15 years to 20 years, in an effort to lower the prices it needs to guarantee developers.

The wind energy industry has faced rising costs over the past few years because of strained supply chains and higher interest rates, meaning many developers need higher guaranteed prices in order to finance their projects.

The Department for Energy Security and Net Zero (DESNZ) stressed that the maximum price allowed was not a prediction of the prices that would be fixed as a result of the auction, because developers often bid below the maximum price to try to win contracts.

A DESNZ spokesman said: “The only way we can get bills down for good and protect families and businesses from volatile gas prices is by moving to a clean power system with homegrown, secure power that we control.

“The reforms we announced last week that include increasing the number of projects to enhance competition will help to drive down prices, securing a positive outcome for consumers.”

The department added: “The ASP [administrative strike price, ie the maximum price] is not a prediction of price – the auction will reveal the true price, just like it did last year, where the auction cleared at prices significantly lower than the ASP.”

The department added that the maximum price would also be “less relevant” than in previous auctions because of technical changes to the way the auction would be run.

The Energy Secretary will be able to see the price of bids during the auction providing further protection for consumers and putting value of money at the heart of the auction.

Desnz said this will help balance the deployment we need to deliver Clean Power by 2030 with getting a good deal for billpayers.