Amnesty International has started disciplinary action after a senior official sent an offensive tweet about three Jewish MPs.

Kristyan Benedict, the charity’s campaigns manager, took to Twitter during a Parliamentary debate about the violence in Israel and Gaza.

He wrote: “Louise Ellman, Robert Halfon and Luciana Berger walk into a bar…each orders a round of B52s … #Gaza”

The B52 cocktail was named after the long-range US bomber and contains shots of coffee liquor, Baileys and brandy.

The tweet was criticised by Amnesty’s campaigns director Tim Hancock. He said: “We do not believe that humour is appropriate in the current circumstances, particularly from our own members of staff.”

Fellow Twitter users had immediately criticised Mr Benedict for targeting only Jewish MPs, and asked why he had not named any of the non-Jewish parliamentarians who had defended Israel during Tuesday’s debate.

In a later tweet Mr Benedict said he had thought the initial message was a “giggle” and “light-hearted… some didn’t – so apols to those who booed”.

He also linked to a second message he had posted which stated: “Those justifying the killing of civilians need to spare me the sanctimony – you know who you are #Gaza #Israel (and #Syria for that matter).”

Mr Hancock said Mr Benedict’s “joke” had been “a private tweet, sent from a private account”, but confirmed an “internal and confidential process” was underway.

He added: “Amnesty International UK, like the rest of the Amnesty movement, is concerned about the loss of life in Israel and Gaza and the potential for escalation. We urge restraint and the utmost respect for human rights and international humanitarian law by all concerned.”

In a letter to Amnesty International chief executive Patrick Holmes and director Kate Allen, John Mann MP said the tweet had “crossed the line between legitimate criticism and antisemitism”.

Mr Mann, chairman of the All-Party Parliamentary Group against Antisemitism, asked the charity to explain what its policies were on antisemitism, what training staff receive on racism and whether it would be prepared to receive assistance in dealing with antisemitic discourse from “experts in the field”.

It is not the first time Mr Benedict has made controversial remarks. In April last year he told a pro-Israel blogger: “I will smack you in your little bald head. You’ve got that on record? I could do if I wanted to, couldn’t I? Put it on your website.”

Amnesty took disciplinary action following that incident and Mr Benedict apologised, saying his actions had been “regrettable”.

The charity was also forced to defend him in July after the Zionist Federation claimed he had “regularly shown a partisan approach” when dealing with Israel.