Labour insiders sense a ‘McDonnell takeover’ as top Corbyn aide quits
Simon Fletcher is said to have become disillusioned by the party's direction.
Jeremy Corbyn's leadership suffered a major blow today as one of his closest aides quit.
Simon Fletcher is thought to have walked out after clashing with shadow chancellor John McDonnell in recent months.
Fletcher ran Corbyn's 2015 leadership campaign and went on to be his director of campaigns and planning.
The 48-year-old - whose job included planning Labour's campaign for the next general election - rose to prominence as chief of staff to Ken Livingstone when the left-winger was mayor of London.
McDonnell and Fletcher are understood to disagreed over the direction of travel for the Labour party, with the shadow chancellor accused by some of orchestrating an anti-Fletcher whispering campaign.
One Labour MP told PoliticsHome the resignation was a victory for McDonnell and his allies.
The parliamentarian said: "The McDonnell takeover is almost complete, he's seen off his old enemy Ken Livingstone and the influence of his allies - first Neal Coleman, then Anneliese Midgeley and now Simon Fletcher.
“The hardliners are now fully in control and the people who ran Jeremy's 2015 leadership campaign have all gone or have no influence.
"The only one left in position is Jeremy himself, and McDonnell is coming for him too."
Another insider said Fletcher's departure cemented the position of Karie Murphy, the director of Corbyn's office and a close friend of Unite general secretary Len McCluskey.
The news was revealed by Evening Standard. A Labour spokesman later confirmed that Fletcher was leaving to "take on other projects and opportunities".
Fletcher's resignation comes just a week after Jon Trickett was dumped as Labour's general election co-ordinator, and replaced by Andrew Gwynne and Ian Lavery.
Trickett tweeted that he was sorry to see "my friend and comrade" Fletcher leave.