Andrew Fisher, Jeremy Corbyn's head of policy, suspended from Labour Party
Jeremy Corbyn's head of policy Andrew Fisher has been suspended from the Labour Party following complaints that he campaigned for a rival party in the general election.
The Labour leader said he continues to have "full confidence" in Mr Fisher, who is understood to remain a member of Mr Corbyn's office.
Labour's ruling National Executive Committee (NEC) has been asked to draw up a report, which could result in disciplinary action against Mr Fisher.
A number of Labour activists and MPs are understood to have made complaints over allegations that Mr Fisher urged supporters to vote for a Class War candidate against Labour's Emily Benn in the Croydon South seat in the May election.
A Labour Party spokesman said: "Andrew Fisher has been suspended from the Labour Party. The NEC will now be asked to authorise a full report to be drawn up with recommendations for disciplinary action if appropriate."
Mr Corbyn said: " I have full confidence in Andrew Fisher and his work. I respect the integrity of the General Secretary's office and trust that this matter will be settled as quickly as possible."
Ms Benn - the granddaughter of Labour's former Cabinet minister Tony Benn - made a formal complaint about Mr Fisher after he sent a tweet in August last year, which read "FFS if you live in Croydon South, vote with dignity, vote @campaignbeard" - a reference to the Twitter account of Class War parliamentary candidate Jon Bigger.
Labour's rule book states that any member who " supports any candidate who stands against an official Labour candidate... shall automatically be ineligible to be or remain a party member".
Mr Fisher last week wrote to Labour's general secretary Iain McNicol to "completely and unreservedly" apologise for the tweet, which he claimed had been "misinterpreted".
He wrote: "I obviously do not and did not support Class War in any way, let alone in an election. I was and am committed to the election of a Labour government and a successful and united Labour Party."
Mr Fisher continued: "I accept that the tweet has been misinterpreted and has caused embarrassment and understandable upset among party members, which I regret.
"I wish to completely and unreservedly apologise for this tweet. I have now closed my social media accounts and assure you there will be no repetition of such activity in the future."
The message about Croydon South is not the only controversial social media post made by Mr Fisher, who also described Ed Miliband's frontbench as "the most abject collection of complete s***e" and celebrated Ed Balls's general election defeat.
Mr Fisher said it was "fitting that the architect of Labour's miserable austerity-lite economic policies should lose #Balls".
David Cameron taunted Mr Corbyn over Mr Fisher's left-wing reputation at Prime Minister's Questions in the House of Commons this week, branding the former union official a "Trotskyist".
The Prime MInister told MPs: "His media adviser is a Stalinist, his new policy adviser is a Trotskyist and his economic adviser is a communist. If he is trying to move the Labour party to the left, I would give him 'full Marx'."
Founder of the Left Economics Advisory Panel, Mr Fisher is the author of The Failed Experiment, which argues that over the past 35 years, governments of all political stripes have "ceded power over fundamental sectors of our economy to a new oligarchy of corporations", while government has become "the servant, not the master, of corporate interests".
The ruling was welcomed by Labour MPs Caroline Flint - who quit the shadow cabinet when Mr Corbyn became leader - and Siobhain McDonagh.
"These rules must apply equally to all members whether they deliver leaflets, are elected representatives or are staff in the leader's office," they said in a joint statement.
"On behalf of those hard working members who were offended by Mr Fisher's activities which included supporting a candidate against Labour in May, it is only right that the general secretary has initiated an inquiry."