One of Jeremy Corbyn’s closest aides has reportedly resigned, issuing a warning that the Labour leader will not win the next general election.

Andrew Fisher, head of policy and the author of the party’s last manifesto, is said to have walked out last Saturday.

The Sunday Times reports he denounced Mr Corbyn’s team for their “lack of professionalism, competence and human decency” in a memo seen by the paper.

Jeremy Corbyn
Jeremy Corbyn is said to be feeling the pressure, as his party gathers in Brighton (Gareth Fuller/PA)

He also said he was sick of the “blizzard of lies and excuses”, and claimed a “class war” had gripped the upper echelons of the party.

His resignation will be a significant blow to 70-year-old Mr Corbyn, who, it is claimed, may also stand down because he feels under “incredible pressure”.

A Labour source said: “We don’t comment on staffing matters.”