Len McCluskey, general secretary of Unite, has attacked his "old friend" Angela Eagle for leading a "squalid coup" and "cowardly attack" on Labour leader Jeremy Corbyn.
The leader of the country's biggest trade union said "powerful interests" were behind the "attempted political lynching" as he confirmed Unite "would stand by Jeremy".
He urged the party's overwhelming majority of rebellious MPs to "re-establish mutual respect and unity" in a speech that targeted Labour challenger Eagle directly.
Let me ask Angela Eagle, who I regard as an old friend, but who resigned as shadow business secretary, a question: did you give 30 seconds' thought as to how this would help the workers at Tata, fighting for a future made still more uncertain by Brexit? Or the oil and gas industry facing obliteration? Or have they been abandoned in their moment of need?
Our movement is divided - bitterly and unnecessarily. Jobs are in jeopardy and long-established rights could be under threat. Millions of working people are looking for urgent answers to the crisis engulfing us. Our members and many besides are looking for a way forward.
Just a year after being elected, a Government rudderless and to blame for dispatching the country, via an unprepared referendum, into a pit of uncertainty. How ironic that a manoeuvre designed to overcome Tory divisions has ended up creating the mother of all splits.
The leader of the UK's biggest trade union has said the country is 'riven' as a result of the EU referendum.Read the full story ›
Len McCluskey told ITV News that the trade unions can help broker a peace deal and reunite the party now the "coup has failed".Read the full story ›
Leaders of 10 unions say pulling out of the EU will allow the government to dismantle hard won workers' rights.Read the full story ›
Jim Murphy launched a broadside attack on Unite boss Len McCluskey as he announced he will resign as leader of the Scottish Labour party.
Mr Murphy said that while trade unionists were "a source of enormous strength and moral purpose" to Labour, the party should not be beholden "to one man."
One of the things about stepping down is that you can say things in public that so many people in the Labour party only say in private. So whether it's in Scotland and the contest to come across the UK. We cannot have our leaders selected - or de-selected - by the grudges and grievances of one prominent man.
The leader of the Scottish Labour party doesn't serve at the grace of Len McCluskey. And the next leader of the UK Labour party should not be picked by Len McCluskey.
The head of the Unite union, Len McCluskey, has arrived at the Grangemouth plant to join local union leaders in the talks on the future of the petrochemical plant and oil refinery.
He denied that his appearance was an admission that his union had failed its members over the dispute, insisting he was "here to save the plant."
A new ruling in force from today means that workers will have to pay up to £1,200 to launch a tribunal claim against their employers.
A protest against the ruling, organised by the GMB trade union, will be held outside an employment hearing in Central London today.
Unite leader Len McCluskey described the ruling as taking “a sledgehammer to workers’ rights”.
Supporters of the ruling say that along with a "remission scheme" for those on a low income, it will help stem running costs of the employment tribunal system, which came in at more than £74.4 million last year, at a cost to the taxpayer.