Ed Miliband has been unrepentant this morning in defending himself from union criticism.
He insists he is "right" to say Labour can't promise to reverse Government spending cuts - including going along with the public sector pay freeze.
The latter point has caused most anger among the brothers. First Unite's Len McCluskey warned the party was on the road to electoral disaster and even "destruction" with its reversion to "discredited Blairism", then GMB head Paul Kenny gave credence to the warning by threatening to sever his union's ties with the party in a letter seen by the Standard.
If GMB walked away, which could only happen if its members approved, the central Labour Party would lose more than £1 million of funding a year. If Unite followed suit, Miliband would goodbye to a further £4 million - plunging the party into financial ruin.
But here's the dilemma for Miliband - if he faces down the brothers who delivered him the leadership, it will allow him to shake off the "Red Ed" tag and really stamp his leadership on the party. It's a tactic which worked so well for Tony Blair, who gambled the farm on scrapping Clause IV and won.
Judging by the reaction of people around Miliband, they are happy for their man to stick publicly to his guns and are bullish about the chances of unions walking away.
"They will stand up for their members, we will stand up for the majority of people in this country," one source said.
A shadow cabinet minister privately acknowledged that unions withdrawing their funding would be a "disaster" - not just for Labour but for the unions too. "They'd never carry it with their members," the frontbencher predicted.
They're probably right, and it might not come to that in any case. But after a start to the year which has seen miserable poll ratings, a race row sparked by Diane Abbott and outspoken criticism from his former guru (among others), I'm sure Miliband could have done without this latest set of negative headlines.
For the record, here's the full text of the letter sent by GMB general secretary Paul Kenny to senior officers at the union yesterday.
The speech Ed Balls made on Saturday may have a profound impact on our relationship with the Labour Party.
I have turned down dozens of offers to comment on TV, Radio and in the Press.
Unite and Unison have adopted similar positions. I have spoken to Ed Milliband and Ed Balls to ensure they were aware of how wrong I think the policy they are now following is.
It is now time for careful consideration and thought before the wider discussion begin on the long term implications this new stance by the Party has on GMB affiliation.
It will be a fundamental requirement that the CEC and Congress determine our way forward after proper debate.
I will update everyone as events unfold but I have to say this is the most serious mistake they could have made and the Tories must be rubbing their hands with glee.
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