The internal strife that Labour avoided after its 2010 defeat has erupted in recent days, with a ferocious contretemps between Len McCluskey and Jim Murphy. In his resignation speech as Scottish Labour leader, Murphy denounced the Unite general secretary as the "kiss of death" for the party, adding that he and his union were "the type of people who could back the wrong horse in a one horse race." McCluskey has since warned that Unite may disaffiliate from Labour if it does not elect "the correct leader" (he is likely to endorse Andy Burnham).

Now, in an exclusive interview with the New Statesman, Tom Watson, the frontrunner to become deputy leader, has appealed for calm. He told me:

I'm very concerned about big personalities in the party slugging it out, I'm worried about this argument between Jim Murphy and Len McCluskey because what I actually want to see is ideas surfacing here. The trade unions for 115 years have been the transmission belt between ordinary people and our political representation in parliament and it's actually stood us in good stead over many years. To have these seismic rows is not doing anyone any good, so I would hope that we can have a sensible debate about party reform and how we can engage trade unionists in the future.

On McCluskey's warning of disaffiliation if the wrong leader is elected, Watson, a friend of the Unite head, said: "In all candour, I don't think it was helpful. There's been tensions between Jim Murphy and Len McCluskey, in particular, for some years now. For me, I just want to get beyond that. When you look at Scotland, we need a six per cent swing to win two seats. There are very big problems that need resolving in Scotland and I have some ideas for them. I want us to get beyond this row and talk about what a model of reform might look like."

He added: "A lot of people are hurting at the minute, we lost a lot of good colleagues north of the border. I would hope that the energy would be channeled positively, rather than negatively".

The full interview with Tom Watson will appear in this week's NS.