The now-deleted retweet on Councillor Michael Green's account

Councillors and members of the public were shocked and left “visibly upset” at Wednesday’s South Ribble Council’s meeting, after it was revealed that Tory Councillor Michael Green had retweeted a photograph of saluting Nazis and Adolf Hitler, stating: “#Lab18 is starting tomorrow and an early Momentum fringe meeting is underway in the hall”.

Opposition leaders said the council's leader, Mary Green, who is also Michael's mother, failed to sanction her son, but she claims an investigation has been launched and the furore was an orchestrated move against her.

Their action has been condemned by the leaders of both the local Labour party and the Liberal Democrat groups, whose mother-in-law was forced to work across Europe by the Nazis and arrived in the UK as a refugee from the Soviet Union.

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Councillor Paul Foster, Leader of the Labour Group, said: “I am disgusted at the events. That tweet is highly offensive."

He added: “We are today therefore calling for the leader to immediately resign, and both her and her son should be expelled from the Conservative Party, there is no place for this type of appalling behaviour.

I am also today writing to the council’s legal officer. We should not have to put up with this type of abuse, there is no place for it in society.”

Councillor David Howarth, leader of the council’s Liberal Democrats, said: “It’s approaching Remembrance Sunday and a cabinet member for Lancashire County Council and former cabinet member for South Ribble, seems to think this is appropriate.

Council leader Councillor Mary Green

“My mother-in-law arrived in this country as a refugee from the Soviet Union, having been forced to work across Europe by the Nazis, and I find this kind of thing absolutely atrocious.

“When questioned as leader, Mary Green then stated her mother arrived in this country after the war with scars from the war, so I asked her what she would think of her grandson.”

Yesterday Councillor Mary Green said: “They’re (Labour and the Lib Dems) putting a slant on this, and that slant is not the truth. It’s clearly been orchestrated before the meeting.

“I’m not prepared to say anymore at this time, but it is a matter that we will be looking at deeply through the council’s administration.”

Labour leader Coun Paul Foster

Solicitor Coun Micheal Green has been approached for a comment.

He is currently Chairman of the local South Ribble Conservative Association. He has represented the Moss Side ward for South Ribble Council since 2003, and is Lancashire County Council member for Moss Side and Farington, as well as cabinet member.

It is not the first time he has come in for criticism over his use of Twitter.

In 2012, he was called on to resign after controversial comments he posted online referring to then-Deputy Prime Minister Nick Clegg flying a gay pride flag over Whitehall.

Lib Dem leader David Howarth

Coun Green wrote: “Gays and lesbians can do what they wish behind closed doors, but I disagree with Deputy PM over flying gay pride flag.”

He was blasted by hundreds of Twitter users for being ‘homophobic’.

David Whelan, monitoring officer at South Ribble Borough Council said: “We have robust policies and procedures in place, and any complaints received against

Councillors will be thoroughly investigated and assessed against our Code of Conduct.”

South Ribble Council's chief executive, Heather McManus, was absent from the meeting on Wednesday as she is on short-term sick leave.