Marriage Alliance spokesperson Sophie York put her proverbial foot in it during the secret meeting of groups opposed to same-sex marriage in Sydney last week, calling marriage equality supporters the “Pagan Caliphate” –which ruffled the feathers of Muslim leaders present.

The meeting on September 20 was due to be held at the Mercure Sydney International Airport Hotel, but it had to be moved because threatening phone calls were made to hotel staff. Instead the event was moved to another location in Sydney’s CBD.

According to a source who was at the event, more than 100 people turned up — mostly older men from the various religious organisations that will be part of the No campaign in the increasingly unlikely event of a plebiscite on same-sex marriage.

[Not-so-accidental death of a plebiscite: how the right killed their own idea]

According to the source, former Liberal candidate and Marriage Alliance spokesperson Sophie York stood up and denounced people who supported same-sex marriage and wanted everyone to be “PC”, which York said “stands for ‘Pagan Caliphate'”. Polygamy was also disparaged during the event as a consequence of allowing same-sex marriage to be legalised in Australia.

This annoyed several of the Muslims in the room for the event, according to the source. The president of the Australian Federation of Islamic Councils, Keysar Trad, who was at the event, confirmed York’s comments and told Crikey that during the Q&A he stood up and stated that the caliphate was part of Islamic history and was not a pagan institution.

He also said that the Australian Christian Lobby had stated in the past that marriage equality would bring calls for polygamy to be made legal, and while he was not asking those in the room to support polygamy, groups should not be mocking or attacking aspects of each other’s traditions to justify their position on the issue of marriage equality.

He said the MC had responded that no offence was intended. We approached Marriage Alliance for comment but received no response.

The Australian Christian Lobby’s omnipresent managing director, Lyle Shelton, was also at the event, and copies of Dr David van Gend’s anti-marriage equality book Stealing from a Child were given out.

[Five ways to make the marriage equality plebiscite suck less]

Tensions between the Christian and Muslim groups in the anti-marriage equality side could be an ongoing problem in the No campaign. Van Gend has previously glowingly quoted an academic describing “jihadi terror” as “a manifestation of Islamic theology”.

Van Gend — who complained of censorship because a printer refused to publish book — also made vague threats to sue BuzzFeed journalist Lane Sainty at his book launch this week because of her report on his comments that marriage equality advocates were “playing the suicide card” in arguing against the plebiscite on the grounds of the mental health impact it would have on LGBTI youth.

The No campaign against same-sex marriage so far seems to focus on the perceived “consequences” of marriage equality legalisation, linking the proposed change to surrogacy laws, anti-discrimination law changes, and the Safe Schools program.