THERESA May’s promise to end austerity is a “complete con,” Labour’s shadow chancellor has claimed.

During her speech to the party faithful in Birmingham, the Prime Minister said the Government would start to increase public investment, and end the decade of Tory spending cuts.

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“When we’ve secured a good Brexit deal for Britain, at the spending review next year, we will set out our approach for the future,” she said. “A decade after the financial crash, people need to know that the austerity it led to is over and that their hard work has paid off.

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“There must be no return to the uncontrolled borrowing of the past. No undoing all the progress of the last eight years. No taking Britain back to square one.

“But the British people need to know that the end is in sight. And our message to them must be this: we get it.”

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McDonnell took to Twitter to rubbish May’s promise.

“May’s claim that this is an end to austerity is a complete con,” he said. “The Tories have promised this before – and it was a con then too. The Government has already told us that spending for the next four years will be hit by many more vicious cuts. Nothing, sadly, has changed.”

Other opposition spokespeople hooked their criticism of the speech on to the Prime Minister’s decision to boogie on to stage to Abba’s Dancing Queen.

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SNP Westminster leader Ian Blackford accused May of having “danced around the key issues,” namely “the disastrous impact of Tory austerity and a Tory hard Brexit.”

“If Theresa May genuinely believes that the UK’s best days lie ahead then she is being wilfully blind to that reality,” Blackford claimed.

Vince Cable, who was commended for his foxtrot on Strictly Come Dancing’s Christmas special in 2010, said: “As somebody who takes dancing seriously, I was delighted to see Theresa May show that she is developing her new hobby. But she was dancing on the head of a pin, confronted by an audience full of people plotting to oust her.”

Scottish Green co-convener, Patrick Harvie, raided the full back catalogue of Agnetha, Benny, Bjorn and Anni-frid for his put down.

“Theresa May sees herself as a Dancing Queen, but that speech was more of an SOS”, he japed. “In what could be the Prime Minister’s final party conference speech, there really was no indication that the UK Government is any closer to striking a Brexit deal,” he said.

Before the Prime Minister even got on stage, she was under pressure, with one of her former ministers calling for a leadership contest.

James Duddridge, former parliamentary under-secretary of state in the Foreign Office, confirmed he had submitted a letter to the backbench Tory 1922 Committee, saying he had no confidence in May.

In his email he wrote: “We need a strong leader, someone who believes in Brexit and someone to deliver what the electorate voted for.”

But there was no agreement from West Aberdeenshire and Kincardine MP Andrew Bowie, who tweeted that May’s speech was “inspiring.”

“Offering hope, opportunity, a defence of capitalism and how, united, our country can be confident in our future. Knocked it out the park. Brilliant @theresa_may.”