Simon Fletcher has called on Labour to keep "the promise" of Jeremy Corbyn's 2015 Labour leadership campaign in an email to all party staff: "an outward-facing mass movement dedicated to an updated, popular and modern vision of Labour’s values", in what one staffer who recieved the message described as a "veiled" rebuke to the recent direction of the party leadership.

Fletcher was Corbyn's campaign manager in 2015, but was increasingly marginalised throughout 2016, with the 2016 campaign managed by Momentum and John McDonnell, the shadow chancellor.

Saying that Jeremy Corbyn was elected because "Labour members, to whom the Labour party belongs, wanted a challenge to the status quo that so obviously fails the majority", Fletcher closed off by thanking staff and signalling his intention to make "a contribution in new ways from now on".

The full message is below:

Dear colleagues,

I am writing to let you know that I have decided to move on to other challenges and opportunities and will be leaving working for the Labour Party today.

I joined Labour in 1988 and there can be no greater source of pride as a member than to work for the labour movement. Democratic socialist politics is about campaigning to win in order to deliver for the majority and this is what I have been privileged to work on.

As Ken Livingstone’s chief of staff I was part of an administration that applied its mandate to deliver. Massive investment in transport, the introduction of Oyster cards, successfully bidding to host the Olympics, congestion charging and better bus services, free bus travel for young people, the first civil partnerships register, holding the city together in the face of terrorism, record numbers of police, reduced crime, and neighbourhood policing in every ward.

I was first employed on a Labour party campaign in 2004, then working for the party from 2009 on the general election, onto the London Mayoral campaign from 2010-12, and then for Ed Miliband, before returning to work for the party with Jeremy in 2015.

In that time I have met and worked with so many brilliant Labour party staff, politicians and volunteers of all strands of opinion, and been inspired by the extraordinary selfless commitment that motivates so many Labour people to strive for a better society.

It’s my intention to contribute to that shared objective by making a contribution in new ways from now on.

Jeremy Corbyn was elected leader with such a massive mandate in 2015 because Labour members, to whom the Labour party belongs, wanted a challenge to the status quo that so obviously fails the majority. That election was not an isolated event in this country but part of a wider upheaval in the politics of the left. I am proud to have been the campaign director of that leadership campaign, and to have served for Jeremy as his chief of staff and then his director of campaigns.

Like thousands of others I remain committed to the promise of the 2015 Labour leadership campaign: a promise that represents a belief in an outward-facing mass movement dedicated to an updated, popular and modern vision of Labour’s values - doing politics differently and better.

Big thanks to everyone reading this who I’ve been lucky enough to work with at the party over the years.