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Diane Abbott was caught in an embarrassing row today after claiming she had won the official backing of Labour leadership favourite Jeremy Corbyn for her mayoral campaign - only for his team to deny it.

The Hackney MP sent out a text, allegedly from Mr Corbyn, to Labour supporters saying that he wanted her to be the party’s candidate for the City Hall race.

But it backfired after and prompted a furious reaction from his team who fear it could put off other mayoral candidates - and their supporters.

One insider said: “We were surprised to see that Jeremy endorsed Diane. The text wasn’t authorised, we didn’t do that, we didn’t endorse her. We’re absolutely fuming.”

Mr Corbyn, an old friend of the mayoral hopeful, has carried out a number of events in support of her campaign in London including speaking at her fund-raiser and at two rallies, including one on Tuesday night.

However, he is also planning events with other mayoral candidates including Sadiq Khan, one of the frontrunners.

Ms Abbott said: “My understanding was the text was cleared with Jeremy personally.”

But the Standard understands that while the MP’s staff discussed the idea with Mr Corbyn himself, he told them they had to agree it with his campaign team first. They went ahead and released the text yesterday without doing so.

It read: “Hi it’s Jeremy. I want Diane Abbott to be Labour’s London Mayor. She will stand up for London against Tory austerity and can win.”

Earlier, Ms Abbott told BBC Radio: “I was the first to nominate him, I think he’s had a great campaign. I did a big joint rally with him earlier in the week. “

She described a combination of the pair running the Labour party and City Hall as “the dream team”

But mayoral rival and Harrow MP Gareth Thomas said: “He is certainly energising many young people but I don’t see him, I’m afraid, as Prime Ministerial material. But the Labour party needs to make sure there’s a place for the likes of him.”

Tottenham MP David Lammy, who along with Mr Khan nominated Mr Corbyn for the leadership so the party could have the broadest possible debate, denied he regretted his decision now. “He’s an authentic politician, not heavily spun,” he said, before adding he was still undecided about who to vote for.

Just two weeks ago Ms Abbott sought to play down the possibility of Mr Corbyn becoming the Labour leadership frontrunner - although polls now suggest he is the clear favourite to succeed Ed Miliband.

She said: “He’s doing very well and the reason Jeremy is doing very well is the things Jeremy is talking about – peace abroad and social justice at home – are things that chime with Labour party members.” She warned that the “sneering” aimed at Mr Corbyn “doesn’t play well” for the party.