Jennie Formby, the political director of the Unite trade union, has dismissed Tony Blair's latest intervention in the Labour leadership race.
The former prime minister has cautioned against the "Alice in Wonderland" appeal of Jeremy Corbyn and mocked those who have embraced a "politics of parallel reality."
His warning has been backed by fellow candidate Andy Burnham who said the party will have "lost the plot", if they ignore the man who "won three general elections for Labour.
Ms Formby tweeted: "Sorry Andy Burnham; I totally disagree that neo-liberal multi-millionaire war-mongerer Blair has anything useful to say."
"He hasn't said anything constructive or useful so far re leadership campaign, you can't just write off tens of thousands supporting JC", she added.
Labour leadership hopeful Andy Burnham,who has previously criticised Tony Blair for making "dire predictions" about the prospect of a victory for rival Jeremy Corbyn, has said the party would be mad not to listen to the former prime minister now.
Mr Blair has issued a final warning to Labour supporters to reject the "Alice in Wonderland" appeal of Jeremy Corbyn or risk driving the party into an abyss.
Speaking to Sky News, Mr Burnham said: "Tony Blair won three general elections for Labour. If we have got to a point now where the Labour Party says it doesn't want to listen to him then I would think we have lost the plot.
"We have got to listen to people who have been there in the past and seen Labour when it had difficulties in times gone by. People like Neil Kinnock who were there in the mid-1980s when Labour did start fighting itself and left the pitch clear for Margaret Thatcher to bulldoze her way through communities."
"We don't want to go back to that and let the heirs to Thatcher, Cameron and Osborne, do the same", he said.
Tony Blair has issued yet another warning to Labour supporters to reject the "Alice in Wonderland" appeal of Jeremy Corbyn or risk driving the party into an abyss.
Defying appeals from the leadership candidates to resist further interventions, he issued a fresh warning that the party would become unelectable.
Writing in The Observer, the former prime minister said he had as yet failed to understand the "powerful" phenomenon behind Corbyn's popularity and mocked those behind it for embracing a "politics of parallel reality."
All the evidence showed Labour lost the 2015 election because it was "anti-business and too left" and had no credible economic plan, he said.
It is like a driver coming to a roadblock on a road they've never travelled before and three grizzled veterans say: 'Don't go any further, we have been up and down this road many times and we're warning you there are falling rocks, mudslides, dangerous hairpin bends and then a sheer drop'.
In the Alice in Wonderland world this parallel reality has created, it is we who are backward looking for pointing out that the Corbyn programme is exactly what we fought and lost on 30 years ago, not him for having it.
With less than two weeks until the result of the Labour leadership election is announced, Mr Corbyn remains the bookmakers' overwhelming favourite to pull off a shock win.
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Tony Blair has not pulled his punches in a series of attacks on the left-wing candidate for the Labour leadership election.
He told people who wanted to vote with their heart for Corbyn to "get a transplant" in a major speech today, and admitted that even if he could win on a left-wing platform, he wouldn't want to.
Former Labour Tony Blair has argued that the party needs a return to the centre ground.
In a speech this morning, he also said that left-wing candidate Jeremy Corbyn was "the Tory preference" for leader.
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