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John McDonnell has declared he is happy to have a cup of tea with Tony Blair , saying: "We need advice from everybody."

Labour's shadow chancellor said Mr Blair should be tried for war crimes in The Hague in a 2013 interview.

But today he vowed to bury the hatchet with the ex-Prime Minister, despite Mr Blair's hostility to Mr Corbyn, to unite the party after the Copeland by-election.

Tory Trudy Harrison took the Cumbria seat from Labour for the first time in its history last month.

"I think we have all looked over the edge on Copeland and we have decided we need to unite the party now," Mr McDonnell told the BBC's Andrew Marr Show.

"And yes, I will be having a cup of tea with [former Blair ally and Corbyn critic] Peter Mandelson.

"There will be lots of things we agree upon. There will be some disagreements.

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"But I think the most important thing that we have got is a responsibility to our party but more importantly to the country."

Asked if he would do the same with Tony Blair , he said: "Of course, I am willing to talk to anybody. We need advice from everybody."

Mr McDonnell said in a 2013 YouTube interview: "I've been supporting the campaign where we've been seeking to arrest Tony Blair every time he comes to this country.

"We believe he should be brought before The Hague and I fully agree with that."

The charm offensive also comes despite Mr McDonnell pointing directly to Lord Mandelson as he defended his claim there was a "soft coup" in the party.

He said some people were "stirring" ahead of the Copeland vote, and pointed out that Lord Mandelson said he was "working every day" to topple Mr Corbyn with phone calls and e-mails.

Mr McDonnell added: "There must have been people on the end of that line and the end of that email chain to receive it."

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Elsewhere the shadow chancellor comprehensively ruled out ever standing again for the Labour leadership.

Talking about himself in the third person, he said: "I want to be absolutely clear: John McDonnell will not stand for the Labour leadership ever in the future again, full stop. I have made that clear time and time again."

He added: " Jeremy Corbyn will lead us into the next election.

"Of course we are building up a succession for the long term future and we have got some really great young talent coming through but they need more experience before eventually they will succeed."

Speaking just days before the 2017 Budget, Mr McDonnell appeared on the BBC immediately before Tory Chancellor Philip Hammond - who refused Labour's call to publish his tax return.

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The millionaire Chancellor snapped: "This demonstration politics isn’t helping to create a better atmosphere in British politics."

Mr McDonnell accused his Tory rival of "running scared".

He claimed he had hoped for a head-to-head at the end of the Marr show to challenge the Tories' refusal to increase 165,000 people's disability benefit in line with a court ruling.

But a Labour source said Mr Hammond's team had refused the "sofa clash" by claiming he needed to travel to ITV's nearby studio for his next interview.