A Christian advocacy group fears for the future of religious liberty in Britain as the Government lifts the ban on same-sex civil partnership ceremonies in churches.

Equalities minister Lynne Featherstone was to confirm today that the ban will be lifted on December 5 in a move that has the full backing of Prime Minister David Cameron.

She insisted that churches would have the freedom to decide if they want to offer same-sex services.

Christian Concern said that even if the scheme was initially voluntary, churches that do not agree to offer the services are “likely to be put under huge pressure to change their policy by campaign groups”.

The organisation said it was “almost certain” that homosexual campaigners would take legal action against churches that refuse.

Chief Executive of Christian Concern, Andrea Minichiello Williams, said the change could “open the door towards severe restrictions on religious liberty” and see pastors and vicars forced to undertake the ceremonies against their beliefs.

“In no way are there sufficient protections for those who object on the grounds of conscience to providing this service,” she said.

“Churches will inevitably be coerced into performing these ceremonies, and those that don’t will be vilified and sued.

“Nobody will seriously believe the Government’s assurances to the contrary, given the way in which previous assurances on civil partnerships have been shattered.”

The move comes not long after the Government confirmed it was committed to changing the legal definition of marriage to include homosexual unions.

Ms Williams said the Government was forcing the redefinition on all of society “whether they want it or not”.

“Such a redefinition will affect the whole of society profoundly, and has severe repercussions for the family,” she said.

She added: “The church at large needs to wake up very fast, or else church leaders who believe that marriage is between a man and a woman may well lose their liberty to continue acting according to that belief, and may be forced in the future to resign their positions.”