In the dying days of the last Labour government, Peter Mandelson regularly acted as Gordon Brown's life-support machine, so it's startling to see him now admit that the party would have performed better under a different leader.

In an interview in today's Guardian, he tells Patrick Wintour:

If you really force me, I think probably it would make a 20 to 30 seat difference to the result. They would have gone to 280 and we would have gone up to 270. They probably would have been the largest party, but not by a decisive margin.

Had the election result been that close, Labour would have had a far better chance of forming a "progessive coalition" with the Liberal Democrats. So what prevented Mandelson from administering the last rites to Brown?

He explains:

It was also my guess that if Gordon stepped down and people got behind David Miliband, Ed Balls would have entered the contest, and before you knew where you were there would have been an ugly fight, not just between two people perceived to represent new and old Labour, which was the last thing we want.

So was it Mandelson's fear and loathing of Balls that cost Labour the election? Perhaps, but his other explanation is more persuasive:

I felt a sense of personal loyalty [to Brown]. I felt a real bond between us and I was not going to be shaken on that.

Mandelson, as he once famously phrased it, regards himself as "a fighter, not a quitter". But on this occasion, he picked the wrong battle.

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