A conservative Christian lobby group is campaigning with Muslims in Labor-held seats to "stop the godless from making sweeping changes" to religious freedoms.

The Australian Christian Alliance has held two NSW rallies in federal Labor seats in the past month, joined by hundreds of Muslim supporters. It plans to hold another rally in the seat of Fowler before the May 18 election.

Australian Christian Alliance rally in Sydney in May.

The alliance's founder, Vic Meli, said the group's members were all Christian but they "worked with and welcomed Muslims and Buddhists and anyone with a common adversity".

"We are determined to stop senior people in Labor who are godless from making sweeping changes to our rights," said Mr Meli, whose group was formed during the same sex plebiscite. "You could say we have joined forces and are working with all faiths."