Shadow Brexit secretary Sir Keir Starmer as warned Labour must not “oversteer” away from the left wing politics of Jeremy Corbyn in the wake of the party’s crushing general election defeat.

Sir Keir, who confirmed he was “seriously considering” a run for the leadership, said Mr Corbyn had been right to make Labour an “anti-austerity” party.

In a clear attempt to distance himself from the legacy of Tony Blair, he said the party could not afford to go back to “some bygone age”.

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His intervention came as the former prime minister delivered a crushing verdict on Labour’s election performance, saying the party had gone into the contest with a “strategy for defeat”.

Labour Tony Blair, delivering a speech in London, has blamed Jeremy Corbyn for Labour’s election defeat (Yui Mok/PA)

In a speech in London, Mr Blair laid the blame firmly at the door of Mr Corbyn, saying he had pursued a policy of “almost comic indecision” on Brexit which managed to alienate both sides of the debate.

“I believe with different leadership we would have kept much of our vote in traditional Labour areas,” he said.

“He (Mr Corbyn) personified politically a brand of quasi-revolutionary socialism, mixing far left economic policy with deep hostility to Western foreign policy which never has appealed to traditional Labour voters and never will appeal to them, and represented for them a combination of misguided ideology and terminal ineptitude that they found insulting,” Mr Blair said.

Mr Corbyn came under fierce attack when he addressed a meeting of the Parliamentary Labour Party on Tuesday, with a number of MPs angrily blaming him for their worst election performance since 1935.

However, Sir Keir, who is seen as coming from a more centrist tradition than the Labour leader, said it would be a mistake to simply abandon his radicalism.

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“What Jeremy Corbyn brought to the Labour Party in 2015 was a change in emphasis that was really important – a radicalism that matters,” told the BBC Radio 4 Today programme.

“We need to build on that rather than simply say ‘Let’s now oversteer and go back to some bygone age’. We need to build on that radicalism.

“What we mustn’t do is say now, because we have lost in 2019, that move to an anti-austerity party has got to be rejected and we go back to some other political place that we were in in the past.”

Sir Keir’s comments will be seen as a pitch to win support from left wing grassroots members who propelled Mr Corbyn to the leadership in 2015 and who remain a significant force within the party.