A group representing 15,000 Christians is taking the Northern Ireland Secretary Peter Hain to court to try to block new gay rights legislation.
New gay rights legislation is to be challenged in court
The regulations will outlaw discrimination in the provision of goods, services and education on the grounds of sexual orientation.
Colin Hart, of the Christian Institute, said the concerns of religious people had been "trampled over".
"The regulations bear all the hallmarks of a rushed time-scale," he said.
"They almost appear to establish a right for homosexuals not to be disagreed with."
Mr Hart said the regulations would give preferential status for gay people.
"It is a preferential status which will drive a coach and horses through religious liberty," he said.
"We're taking action to protect the many Christian people in Northern Ireland who will become victims of frivolous accusations if these regulations become law."
On Monday, an NI assembly motion condemning the government's plans fell after a tied vote.
After a two-hour debate at Stormont, 39 assembly members voted in favour of a DUP motion and 39 against.