TRADE union chief Len McCluskey has offered to “broker a peace” between Jeremy Corbyn and his Labour opponents at Westminster to avoid a full-blown civil war, which could mean the party would never unite again.

The general secretary of Britain’s biggest trade union and the party’s largest donor, who is a leading supporter of Mr Corbyn, decried the “orchestrated coup” attempt by some Labour MPs, 80 per cent of whom voted against their leader in a motion of no confidence last week.

"This has been a political lynching of a decent man; undermined, humiliated, attacked in order to push him out,” declared Mr McCluskey on the BBC's Andrew Marr programme.

"And here's the truth; it's failed. The coup has failed. Jeremy Corbyn is made of stronger stuff; he is a man of steel and he has made it clear that he will not step down."

The union leader said he had been amazed by the actions of some right-wing MPs and claimed "sinister forces", including a PR company with links to Tony Blair, had "seduced" them into opposing their leader.

Describing the trade union movement as Labour’s rock in stormy seas, he offered to "broker a peace" with Mr Corbyn remaining as leader as he urged potential challengers Angela Eagle and Owen Smith to “desist from this” and step back from opposing the leader.

"The alternative if Angela goes ahead with this, and I hope she doesn't, or Owen, is that we are plunged into a civil war that will be bitter and ugly and may never allow the Labour party to reunite again," Mr McCluskey said, adding; “Give us a chance[to]...resolve the issues.”

John McDonnell, the shadow chancellor, suggested Mr McCluskey’s offer to meet and talk should be taken up as he decried Mr Corbyn’s critics of a “divide and rule” strategy, which had brought politics into the gutter. The party leader has himself said he is now “ready to reach out” to his critics but warned them that if there were a leadership challenge, he would stand.

Earlier, Lord Kinnock claimed support for Mr Corbyn outside Westminster was seeping away and there was "no basis" on which he could stay in post.

The former Labour leader said party rules meant Mr Corbyn could not continue in the party's top job because he did not have the required “substantial support” from MPs as required by the party’s constitution; he would also need to secure backing from more than 50 MPs if he wanted to fight a leadership challenge.

The party grandee, who faced a leadership challenge from Tony Benn in 1988, claimed there had been a "significant shift away from Jeremy" in recent days.

He told Mr Marr: "Members across the country, including newly-joined people, have got deep residual doubts about the possibility of him leading the party to election victory and that means he should reconsider his position on those grounds."

Lord Kinnock called on Mr Corbyn's supporters to think about whether or not they wanted to "turn up at the funerals of communities and industries" caused by decades more of Conservative rule.

Meantime, Emily Thornberry, a close ally of Mr Corbyn, urged MPs to "take a step back".

The shadow foreign secretary warned: “The future of the country is at stake here."

She branded as "nonsense" a claim that Mr Corbyn's aides were keeping his deputy Tom Watson away from him because they feared he would try to "bully" the 67-year-old leader into quitting.

Mr Watson has been trying to seek a meeting with Mr Corbyn to find a way of negotiating a settlement as the crisis engulfing the party shows no sign of abating.

Mr Corbyn's team said it had a "duty of care" to the leader and highlighted his age.

Lord Prescott told the BBC’s Daily Politics programme that while Mr Corbyn had been improving in his performance as party leader, he did “not have the passion”.

“A leader's got to reach across the party. I don't think Jeremy's done that," the former deputy prime minister said.

He pointed out how Labour MPs "had to recognise the course” the party was on" and come together to "avoid a civil war".

While he said Mr Corbyn’s name should not automatically appear on a leadership ballot paper, he stressed how he hoped that Ms Eagle and others would not challenge the party leader; instead, MPs should go home for the summer and then return to Westminster with a more unified mindset.

Elsewhere, Tony Blair, who is despised by many of Mr Corbyn's grassroots supporters, refused to be drawn on whether the leader should step down but stressed the Opposition needed "credibility".

Declaring on the Murnaghan programme on Sky News that he had “resolutely refused” to intervene in the leadership debate, the former party leader then said: “For a democracy to function you have got to have an opposition with a minimum level of credibility to challenge Government and to hold it to account.

"Especially at the moment when that 48 per cent is feeling deeply disenfranchised and when there is this huge negotiation of national interest on the table.”

Mr Blair added: "You need to have that and if the opposition is incapacitated it allows frankly what's been happening with the Conservative party to happen because they can do whatever they want because they think they are going to be the government at the end of the day."