Jeremy Corbyn’s closest political ally attended a celebration of Leon Trotsky and praised the “importance” of his ideas, The Telegraph has learnt after the Labour leader dismissed concerns of hard-Left entryism as “nonsense”.

John McDonnell, the shadow chancellor who chairs Mr Corbyn’s re-election campaign, joined socialist activists to commemorate the 70th anniversary of Trotsky's death in September 2010.

Mr McDonnell “spoke about the importance of Trotskyism for the struggle against the bosses and the Tories”, according to an account of the meeting.