Shadow chancellor John McDonnell has triggered a war of words in Labour's ranks after he reportedly branded anti-Jeremy Corbyn plotters as "fucking useless". The left-winger appeared to make the foul-mouthed attack as he addressed a rally of Corbyn supporters in Kentish Town, London, yesterday night (12 July).

McDonnell, a long-time ally of the embattled Labour leader, delivered the speech after Labour's ruling body, the National Executive Committee (NEC), voted 18 to 14 to automatically put Corbyn on a leadership election ballot.

The decision was a blow to anti-Corbyn activists, who were hoping that the left-winger would have to attract 51 nominations from Labour MPs and MEPs to enter the race. The ruling came after only 40 Labour MPs voted against a motion of "no confidence" in Corbyn and followed a string of resignations from his shadow cabinet in protest over his EU referendum campaign performance.

Heidi Alexander, the former shadow health secretary, took to social media site Twitter to brand McDonnell's comments as "awful". She added: "John, I resigned because the whole operation was f****ng useless not because of a plot."

The exchange comes as the Labour Party's turmoil continues, with former shadow business secretary Owen Smith announcing his intention to run in the leadership contest. The Welsh MP will also be up against Angela Eagle, the former shadow business secretary, unless one of the contenders drops out to push a 'stop Corbyn' candidate.

Corbyn is favourite to win the contest after securing almost 60% of the in the 2015 leadership election and enjoying the support of Labour-affiliated trade unions, including Unite, Aslef, TSSA and Unison.

"[The race] will be a democratic debate about the future of our country – where we set out the alternative Labour is offering under my leadership and our plan for government," the Labour leader said in a statement last night.