An internal Labour party argument has broken out which could damage relations between Jeremy Corbyn and one of his earliest and strongest supporters, the First Minister Mark Drakeford.
The Welsh Labour leader has written to MPs to say he's 'deeply disappointed' by a decision taken on Tuesday by the party's ruling National Executive Committee (NEC) not to allow Welsh Labour control over the re-selection of MPs.
Some AMs are also angry after learning of another 'calculated insult' to Mark Drakeford. He's due to speak to Labour's conference in Brighton at 9.50am on Sunday morning, 'the graveyard or Tom Watson slot' as one put it.
The rule change may seem relatively obscure to those outside the party but the move is being seen inside as a deliberate attempt to impose rules on Welsh Labour and 'throwing devolution under a bus' as it was described to me.
And it actually may not be a change seen strictly in terms of the party's rule book. It was generally assumed that Welsh Labour had control over re-selecting MPs just as it does over selecting candidates to be MPs and both things when it comes to AMs.
But with re-selections and trigger ballots proving hugely controversial in the party and one of the fault lines between supporters and opponents of Jeremy Corbyn, it was something that it was decided to address when the NEC met.
Mark Drakeford supported formally devolving the power to Wales as 'a sensible cleaning up of the rules' as did his nominated representative on the NEC, Mick Antoniw. They were overruled.
The practical difference is that there are now likely to be different rules operating in the same constituency parties. So the threshold for triggering a full re-selection of a sitting AM would require 51% of votes from branches and affiliates whereas the threshold to do the same against a sitting MP would only require a third of votes which is the threshold in England.
Some have told me it was done ‘purely for factional reasons’ i.e. to gain control over trigger ballots such as that held against Police & Crime Commissioner Alun Michael this week.
Welsh MPs say that it's not so much the rule itself that they're angry about but that the principle of devolution has been ignored. 'It throws devolution under a bus,' said one.
More worrying for the leader's office will be the response of the Welsh Labour leadership. Mark Drakeford has now written to Welsh Labour MPs saying he was 'deeply disappointed' by the decision and that the Welsh Executive Committee will now consider the implications.
His letter is below:
The First Minister was one of the earliest supporters of Jeremy Corbyn and has spoken strongly ever since both in favour of the Labour leader and the controversial rule changes which his time in office has seen.
Despite that support there's a feeling amongst senior Labour figures that the leader's office 'continues to disrespect the only Labour leader of a government across the UK.'
Perhaps it stems from a difference over Brexit which has emerged. While Jeremy Corbyn has said he'd remain neutral in a second referendum, Mark Drakeford and the Welsh Labour government has been clear they would campaign to remain.
Whatever the reason, a row which risks alienating allies seems a strange one to have on the eve of a Labour conference already likely to be tense.
Some supporters of Mark Drakeford and Jeremy Corbyn see things very differently. One said that the First Minster doesn't see insults in conference speech timings:
Another said the reselection rules are only controversial to MPs and others who feel they're losing control to members:
With a difference of position emerging between the two Labour leaders, Mark Drakeford has moved to make his view and that of Welsh Labour clear.
He's written to all party members in Wales explaining why he'd back remaining in the EU in any future referendum.
A Welsh Labour source insists the timing has nothing to do with Jeremy Corbyn's suggestion that he'll remain neutral and that 'Mark has always intended to reiterate his position this week ahead of conference.'