Sir Keir Starmer has been told by trade union Unite that any plan to block new North Sea oil and gas developments must not leave workers “paying the price”.

Unite, the party’s single biggest donor, told the Labour leader that such a move could risk a “repeat of the devastation” caused by the closure of coal mines.

Sir Keir is reportedly on the verge of announcing the plan when he sets out his net-zero energy policy next month, but the move has prompted a backlash from the party’s trade union backers concerned about the impact on workers.

Graham Stuart, minister for climate and net zero, said earlier this month that the Government is committed to new North Sea oil and gas licences.

Unite general secretary Sharon Graham hit out at Sir Keir on Wednesday and said the proposal lacks crucial details.

“Grabbing the headlines is easy, developing a serious plan for more renewable energy is not,” she said.

“When Keir Starmer decided to let the world know that he would halt new oil and gas production in the North Sea he left out everything that was important – the detail.

“Labour must now be very clear that they will not let workers pay the price for the transition to renewable energy. When it comes to jobs we can’t have jam tomorrow.”

Ms Graham, who heads one of the UK’s largest trade unions, accused the Labour leadership of behaving recklessly by failing to offer a clear plan to protect jobs.

She said such a move by Labour, if not well-thought through, could have the same impact as the mass closure of the coal mining industry in the second half of the last century.

Closures in the 1980s prompted a bitter and protracted stand-off between the Conservatives under Margaret Thatcher and striking miners.

“We cannot have a repeat of the devastation wrought on workers and their communities by the closure of the coal mines. It is reckless in the extreme to talk about halting this industry without offering a coherent, fully funded plan for jobs,” Ms Graham said.

“A workers’ transition plan for the North Sea must involve three things. First, it needs to put workers in the industry, and their communities, front and centre. It must be carried out with their full involvement and guarantee decent jobs for all involved with no loss of pay and conditions.

“Second, it will require substantial investment. We have yet to see Labour, or any political party, commit to the serious amounts that will be needed.”

Ms Graham said her union wants public ownership and democratic control of the energy sector under any changes.

“We cannot trust the private sector, whose only concern is squeezing every last drop of profit out of the UK’s remaining oil and gas reserves, to deliver for workers and communities.

“Britain’s recent economic history is littered with political betrayals and broken promises that have left industrial workers on the scrap heap. That is why workers need to take charge of their own destiny,” she said.

The row with a major party donor comes as Sir Keir also faces questions over donations received from British businessman Dale Vince, who is also a key backer of climate activist group Just Stop Oil.

Mr Vince, the founder of green energy firm Ecotricity, has given around £1.5 million to Labour over the past decade, according to filings to the Electoral Commission.

Tory MPs have attacked Labour over the donations and called on the party to hand the money back.