ED Miliband was under fire last night after suddenly pulling out of a landmark appearance at Durham Miners' Gala - because a union firebrand will share the stage.

The Labour leader was set to turn the page on the era of Tony Blair and Gordon Brown by becoming the first head of his party to attend the celebration - to be held in Durham City, on Saturday, July 9 - for 22 years.

The decision, announced in March, was hailed as evidence of Mr Miliband's determination to rebuild support with traditional working-class supporters - who deserted New Labour in droves.

But now Mr Miliband has performed a U-turn, blaming the organisers' decision to also invite Bob Crow, the far-left general secretary of the Rail, Maritime and Transport union, to speak from the same platform.

Mr Crow is a hate figure for right-wing newspapers, for staging a series of strikes on the London Underground that have caused misery for millions of commuters.

A spokesman for the Labour leader said: "The decision to invite Bob Crow onto the platform at the Gala means Ed is not able to attend this year.

"He doesn't want to share a platform with someone who is not a Labour supporter and who has attacked Labour many times in the past."

However, the spokesman denied the decision reflected reluctance to be linked with Labour left-wingers after recent criticism of Mr Miliband's leadership, saying: "Ed has said he will come next year."

But the rethink was fiercely criticised by David Hopper, general secretary of the NUM in Durham, who denied Mr Crow had used previous appearances to attack Labour's leadership.

Mr Hopper said: "In any case, people should be allowed to speak out if they don't agree with Labour policy. I don't see anything wrong with that - that's democracy, isn't it?

"It's a big disappointment for a lot of people who vote Labour that Ed Miliband won't be coming, but that's for him to decide. I don't know who's advising him."

Mr Hopper revealed that a letter from the Labour leader made no mention of Bob Crow, but blamed "diary pressures" for his non-appearance - a second reason put forward by Mr Miliband's spokesman yesterday.

The last time a Labour leader spoke at the event was Neil Kinnock, in 1989, following in the footsteps of Clement Attlee and Harold Wilson.

Tony Blair shunned the gala during his 13 years as leader, even though his constituency was in County Durham. Towards the end of his premiership, he stopped replying to invitations.

However, one Labour backbencher said Mr Miliband was wrong to say yes in the first place, adding: "You have to sit there, listening to Labour being slagged off. He is right not to go."

Meanwhile, Mr Crow sidestepped the controversy, saying: "It is the greatest honour in the Labour movement to be invited to speak at the Durham Miners' Gala. I am looking forward to making my third appearance on the platform."