In a boost to her campaign, the NUM said the Wigan MP was the candidate Labour needs to “regain trust with the voters we’ve lost” after its disastrous electoral defeat in December.
While the NUM has a small membership, its endorsement is highly symbolic and its decision to back Ms Nandy will come as a blow to Rebecca Long-Bailey, the left-wing favourite who is regarded as the heir apparent to Mr Corbyn.
The move comes after Sir Keir Starmer built an early lead in the contest by winning the support of Unison, the UK’s largest trade union, which represents more than a million public sector workers.
Union support will be crucial to the five candidates vying for Labour’s top job. Party rules say each candidate must win the support of 5 per cent of constituency parties and affiliated groups, including two trade unions, to pass the next hurdle.
Ms Nandy told the Yorkshire Post: “I represent a former coalfield community. I’m really proud of that, and I am really proud to work alongside the NUM since I was first elected.
“Former coalfields and towns are crying out for real change. Some of these areas are part of the famous red wall that fell in the last election.
“I get it. If Labour wants to be part of making that change happen, we have to go back out into our communities and fight for it.”
Chris Kitchen, the general secretary of the NUM, said: “Lisa Nandy is the leader Labour needs to rebuild the party and regain trust with the voters we’ve lost.
“Our executive was pleased the contest has so many outstanding candidates. The NUM is proud to back Lisa.
“She represents a coalfield community, she has stood with us in our fights for justice and regeneration and we are confident she’s the leader who can take Labour back into government once again.”
After Unison, there are four other big affiliated unions, including GMB, Unite, the Communications Workers Union, and Usdaw, which represents shop workers.
The support of Unite, Labour’s largest financial backer, is likely to be decisive. Ms Long-Bailey, the shadow business secretary, is thought to be its chosen candidate but Unite boss Len McCluskey insisted no decision had been made.
Sir Keir, the shadow Brexit secretary, has emerged as an early frontrunner in the race, with Ms Long-Bailey as his main rival, but the contest is still in its early stages.
Prominent backbencher Jess Phillips and Emily Thornberry, the shadow foreign secretary, both won enough support from MPs to pass the first hurdle, setting up for a five-way contest.
The new leader will be announced at a special conference on 4 April, after being elected by Labour members.
Non-members can apply to be registered supporters – costing £25 – over the next 48 hours, which allows them to vote in the contest.