A prominent group of ex-Muslims are facing calls to be banned from future Pride marches in London after a mosque complained about their criticisms of Islam.

Activists affiliated to the Council of Ex-Muslims of Britain (CEMB) took part in the march on Saturday 8 July. Their signs bore slogans such as "Allah is gay," "Throw ISIS off the roof" and "Islamophobia is an oxymoron".

Some listed the 13 countries – all under Islamic rule – where homosexuality is punishable by death. One sign said "Fuck Islamic homophobia," with "Fuck Islam" in a different colour to the rest of the letters.

One banner specifically accused East London Mosque of inciting the murder of LGBT people. The mosque responded by complaining to the event's organisers, who are now considering banning CEMB from future marches.

"We've raised a complaint with the co-chairs of the event that the group was inciting hatred against Muslims," said Salman Farsi, a spokesman for the mosque. He added that the banners had attacked "our good name, based on absolutely groundless reasons".

He said the mosque had publicly condemned attacks on LGBT people and "gay-hate" stickers which were seen in Tower Hamlets several years ago.

But CEMB said the mosque's "supposed track record for challenging homophobia only seems to extend to white gay men in East London and never to Muslim and ex-Muslim LGBT or LGBT persecuted outside of Britain in countries under sharia".

East London Mosque has hosted preachers who have called for homosexuals to be put to death. Other speakers have compared homosexuality to paedophilia, attacked schools for teaching about it and said gay people make them "nauseous".

This weekend human rights campaigner Peter Tatchell said he had asked the mosque to meet LGBT Muslims 11 times since 2015 – and all his invitations had been rejected.

Pride has referred the complaint to its community advisory board. In a letter to the mosque, it said the board would determine "whether CEMB will be allowed to march again in the years ahead".

A spokesman from the event said: "If anyone taking part in our parade makes someone feel ostracised, discriminated against or humiliated, then they are undermining and breaking the very principles on which we exist.

"Pride celebrates diversity and will not tolerate discrimination of any kind. While our parade has always been a home to protest, which often means conflicting points of view, Pride must always be a movement of acceptance, diversity and unity. We will not tolerate Islamophobia."

Maryam Namazie, the ex-Muslim group's spokesperson, said criticism of Islam and Islamism was being "erroneously conflated with an attack on Muslims".

"The very reason CEMB was at Pride was to combat hate. There were some Muslims who were offended by our presence and others who supported us, as there were some Christians who were offended by placards poking fun at Christianity and others who found them funny. This is what real diversity looks like.

"Offence has become the catchphrase to impose de facto blasphemy and apostasy laws here in Britain. The politics of offence rewards bullies and blames victims."

She added that the police had confronted the group over the banners at the march.

The National Secular Society expressed its support for CEMB's right to free expression.

Stephen Evans, NSS campaigns director, said: "The accusation that the group was inciting hatred against Muslims is baseless nonsense. East London Mosque seems to have begun a brazen attempt to deflect criticism of its poor record on gay rights and the repression of LGBT people in much of the Islamic world.

"CEMB has raised awareness of these vitally important issues. We urge Pride's organisers not to place religious ideas beyond criticism, which would be a highly regressive step and contrary to its own spirit of openness and inclusion."

The NSS has campaigned for free speech on religious issues throughout its history. In 2008 the blasphemy laws were officially repealed after a 140-year NSS campaign. In 2013 the Public Order Act was amended so that "insulting words or behaviour" were no longer outlawed.

The society is currently taking a leading role in defending the UN Human Rights Charter against Islamic nations which have called for greater restrictions on speech concerning religion.

Picture credit: © Maryam Namazie, via Twitter