A growing number of US churches, worried they might be sued by gay couples, are changing their by-laws to reflect the view that the Bible allows only marriage between one man and one woman.

In June, the US Supreme Court struck down a provision of the federal Defence of Marriage Act (DOMA) that defined marriage as between a man and a woman for purposes of federal law.

Although there have been lawsuits against wedding industries that refuse to serve gay couples, attorneys promoting the by-law changes say they do not know of any lawsuits against churches.

Recently, however, churches have said that it is only a matter of time before one them is sued.

Gregory Erwin, an attorney for the Louisiana Baptist Convention, said: “I thought marriage was always between one man and one woman, but the Supreme Court in a 5 to 4 decision said no.

“I think it’s better to be prepared because the law is changing. America is changing.”

Kevin Snider, an attorney with the Pacific Justice Institute, a non-profit legal defence group that specialises in conservative Christian issues, said some religious leaders have been threatened with lawsuits for declining to perform at same-sex weddings.

Mr Snider’s organisation released a model marriage policy a few years ago in response to a state-wide same-sex marriage dispute in California.

Dean Inserra, head pastor of the 1,000-member City Church Tallahassee, based in Florida, said he does not want to be alarmist, but his church is also looking into addressing this issue.

Me Inserra said he has already had to say no to gay friends who wanted him to perform at their wedding ceremony.

He said: “We have some gay couples that attend our church. What happens when they ask us to do their wedding? What happens when we say no? Is it going to be treated like a civil rights thing?”

Critics, including some gay Christian leaders, have accused these changes of being solutions attempting to look for a problem.

Justin Lee, executive director of the Gay Christian Network, said: “They seem to be under the impression that there is this huge movement with the goal of forcing them to perform ceremonies that violate their freedom of religion.

“If anyone tried to force a church to perform a ceremony against their will, I would be the first person to stand up in that church’s defence.”

Eric Rassbach, an attorney with the Becket Fund for Religious Liberty, a public interest legal group that defends the free expression rights of all faiths, said it is unlikely the government would try to force a pastor to perform a same-sex marriage.

He added, however, that churches that rent out their facilities to the general public could face problems if they refuse to rent to gay couples.

Although his organisation has not supported the by-laws, he said it could strengthen a church’s legal position to adopt a statement explaining its beliefs about marriage.

“A number of groups don’t have a written doctrine,” Mr Rassbach said. “Say a group like the Primitive Baptists – they don’t want a written-down credo, but the courts like written-down things.”

Mr Rassbach said it was important for churches to get their beliefs in writing before a dispute arises, otherwise it can look to a court as if something was done after the fact as a way to cover up homophobic discrimination.

Earlier this week, Elders at Ridgedale Church of Christ in Chattanooga, Tennessee kicked out a mother who publicly supported her gay daughter.

Linda Cooper was told by her local church in a private meeting, that supporting her gay daughter, Kat Cooper, was contrary to the church’s teachings and she would either have to “publicly atone” or leave the church.