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 shadow chancellor earned loud cheers as he launched an foul-mouthed attack on the MPs seeking to replace his friend Corbyn.
The MP for Pontypridd resigned as shadow work and pensions secretary last month in protest at Jeremy Corbyn's leadership.
I now realise that my earlier description of the NEC meeting - as an omni-shambles - was generous.