The couple drove back home after being refused a room in the B&B
A gay couple are to sue the owners of guest house who turned them away because of their sexuality.
Michael Black and John Morgan, from Brampton, Cambridgeshire, had booked a double room at the Swiss B&B in Cookham, Berkshire, in March.
Owner Mike Wilkinson said he and his wife Susanne stood by their stance and denied being opposed to gay people.
Civil liberties organisation Liberty is acting for Mr Black and Mr Morgan and said it planned to bring a civil case.
Legal director James Welch said the Equality Act (Sexual Orientation) Regulations 2007 made it against the law for public authorities and other service providers to discriminate on the grounds of sexual orientation.
He said: "This isn't about money for them. Their only motive is in order to prove the point that it is unlawful and should not have happened.
"If they win, they have said they will give any money away to charity."
He said the case was as important in principle as that of black US civil rights activist Rosa Parks, who refused to give up her seat on a bus to a white man in Alabama in 1955.
Mr Black, 62, and Mr Morgan, 56, had been in the village, near Maidenhead, to meet some friends for dinner and to see a local play.
At the time of the incident, Mrs Wilkinson told the couple it was "against her convictions" to let them share a bed.
Mr Wilkinson says the couple uphold their position, insisting they were simply adhering to their Christian beliefs.
The couple said they were met outside the house by the B&B's owner
He said: "We are rather surprised that Liberty would be so one-sided in a matter of liberty because there are two liberties to uphold in this case.
"There is a religious liberty to uphold and there is the right for homosexuals to practise what they want to do. We have received the letter from them.
"We don't want to go to court but if they want us to then I suppose we will have to. We are sorry we have offended these guys."
The row escalated during the recent general election campaign when the then shadow home secretary Chris Grayling said people who run bed and breakfasts in their own homes should have the right to reject homosexual guests.
He said he was looking at being "sensitive to the genuinely held principles of faith groups" but was not seeking a change in the law.
Thames Valley Police has recorded the incident as a "homophobic incident".