Church leaders have severely criticised a demonstration organised by right-wing group Britain First over the building of a mosque.

A letter written on behalf of 13 clergy in Burton on Trent, where the march is due to take place, said that they were "disturbed by the intention" of Britain First to protest the proposed building of a mosque in the Staffordshire town. More than 1,600 people have said they are attending the protest on a Facebook page promoting the event.

"We support, under the law, freedom of worship and religious assembly. We support, under the law, the building for that purpose. We also support the right to legal civil protest," the clergy wrote in a letter to the Burton Mail, signed by Rev Michael Freeman of St John the Divine church.

"What disturbs us is the implication that 'Britishness' and Islam should be seen as incompatible. We hope the people of Burton will not let good community relations be damaged by a confrontation with a considerable level of participation from outside our area.

"We offer good wishes to our brothers and sisters in the Muslim community."

Following the clergy's response, Britain First – an offshoot of the British National Party – posted the following to its Facebook page:

Organisers insist that the demonstration will be peaceful, but the there is precedent for violent clashes during similar protests. A march led by far-right group Pegida in Newcastle earlier this year ended with five being arrested after fights broke out.

Despite claims that the new building in Burton will be a 'mega mosque', Muslim leaders have insisted that it will be modest, and built to meet the needs of the local community. There is already a mosque on the proposed site on Uxbridge Street, which will be knocked down to make room for the new building.

Britain First, which calls itself a 'patriotic political party and street defence organisation' has faced significant criticism for what many see as its anti-Muslim stance. Its Facebook page, which has more than 900,000 likes – more than the Labour and Conservative parties combined – regularly posts about the dangers of Islamic extremism, along with Bible verses and calls for Britain to return to its Christian roots.

Over the weekend, Britain First leader Paul Golding announced that he is running for London Mayor.