John McDonnell has said Keir Starmer is making a “mistake” by blocking Jeremy Corbyn standing as a Labour MP at the next election.
Starmer confirmed on Wednesday that his predecessor will be prohibited from running under the Labour banner.
However, the decision has infuriated the Labour Party’s left wing - including Corbyn who accused Starmer of a “flagrant attack” on democracy.
Corbyn lost the party whip in 2020 after he said cases of anti-Semitism in Labour while he had been leader were “overstated” by his political opponents.
The ban came as Starmer welcomed the equalities watchdog’s decision to lift the party out of two years of special measures over its previous failings on anti-Semitism.
McDonnell, who was shadow chancellor under Corbyn’s leadership, said party members should be able to “select the candidates of their choosing”.
He told BBC Radio 4’s World At One programme: “We were created as a coalition of a whole range of different political views, a broad church as we describe it, and the norms of our party, the normative values of our parties, is to have that sort of mutual respect for different views and hold together.
“That includes insuring that we have democratic procedures, where the rights of our party members is to enable them to select the candidates of their choosing, and to undermine that flies in the face of everything that we stand for.
“And that’s why I think it’s a mistake and I think it’s a mistake for Keir to try and bar Jeremy Corbyn from standing. But it’s not just about Jeremy, it’s much more fundamental than that.”
Corbyn’s former shadow home secretary Diane Abbott also rowed in to support him, tweeting: “The Labour members of Islington North CLP get to decide who is their candidate at the next general election - no-one else.
“Otherwise, the party is run by diktat not by its rules and democracy.”
Starmer used a speech on Wednesday to invite his opponents on the Labour left to leave the party which he said is now “unrecognisable” from its form under Corbyn.
“Let me be very clear, Jeremy Corbyn will not stand at the next general election as a Labour Party candidate,” Starmer said in east London.
“What I said about the party changing I meant and we are not going back.”
In a statement on Twitter, Corbyn said of Starmer’s decision: “This is a divisive distraction from our overriding goal: to defeat the Conservative Party.”