UPDATE: A councillor has apologised for tweeting: "Armed Forces Day has certainly brought the hired killers onto the streets of Brighton today".
Green Councillor Ben Duncan, who represents Queen's Park ward on Brighton and Hove City Council, sent the tweet yesterday while the city celebrated war heroes with Armed Forces Day.
Armed Forces Day has certainly brought the hired killers onto the streets of #Brighton today. Hard to explain to my son!
— Ben Duncan (@KemptownBen) June 28, 2014
The comment has provoked an angry response, with people calling for his resignation and labelling him "spineless".
And Green Brighton Pavilion MP Caroline Lucas called on the local party to take disciplinary action against Coun Duncan if he does not immediately apologise.
Ms Lucas also said she had spoken directly to Coun Duncan, and shortly after 11am, he took to Twitter again to apologise.
The original tweet has been retweeted by scores of other Twitter users, including the political blogger Guido Fawkes, who added: