“It’s a huge mistake,” Mr McDonnell told the BBC’s Today Programme on Wednesday. “Our constituents are facing a Universal Credit cut in a few weeks’ time…many of them a public sector pay freeze, energy prices going up, inflation going up and in the real world that’s what we should be addressing.
“Then to go into a Labour conference…and this is the first conference coming together physically as a result of Covid…to then concentrate on internal, factional disputes, it’s just not what people expected from Keir.”
The one member one vote system, introduced by former leader Ed Miliband, is credited with opening the way for Mr Corbyn to seize control of the party in 2015 and laying the ground for a shift to the hard left.
“Our rules as they are right now, focus us inwards to spend too much time talking to and about ourselves and they weaken the link with our unions,” the Labour leader said. “These are two things that have got to change if we are serious about winning the next election.”
But Mr McDonnell said the move risked breaking trust in the leader. He said: “Keir was only elected 18 months ago and he was elected by those people and he never mentioned any of these reforms in that election itself and I think he is opening himself up to charges of dishonesty and if it comes to the point when our own members can’…why do we unnecessarily divide the party in this way.
“What he should be doing is have a proper consultation – he can’t just bounce this through
“Look at the contrast in the media. You have Boris Johnson strutting the world stage, doing deals with [Joe] Biden and other world leaders, what do we have the Labour leader in grubby stitch up deals…it’s unacceptable.”