Christian guest house owners ordered to pay damages after refusing to allow a gay couple to stay in a double room appealed yesterday and told judges that they were entitled to hold "outdated" religious beliefs.

Peter and Hazelmary Bull, who run Chymorvah House in Marazion, near Penzance, said they thought that any sex outside marriage was "a sin" but denied that they had discriminated against Martyn Hall and his civil partner Steven Preddy.

In January, Judge Andrew Rutherford concluded that the Bulls acted unlawfully when they turned away Mr Hall and Mr Preddy, both from Bristol, in September 2008. He decided that the Bulls had breached equality legislation and ordered them to pay the couple a total of £3,600 damages, following a hearing at Bristol County Court. The Bulls asked the Court of Appeal to overturn the ruling yesterday.

Mr Bull, who will be 72 today, and Mrs Bull, 67, were at the appeal hearing in London to listen to lawyers outline arguments.

James Dingemans QC, for the Bulls, told three appeal judges that his clients operated a policy directed towards sexual ''practice" not sexual ''orientation".

"[The Bulls] have operated a policy of restricting the provision of double rooms to married persons," said Mr Dingemans, in written arguments given to judges.

"[The Bulls] maintain that their policy is directed towards sexual practice and not sexual orientation, so there is no direct discrimination."

He said the Bulls were not trying to undermine the rights of Mr Hall and Mr Preddy and judges had to carefully balance all human rights involved.

"The reality of this case is that [the Bulls'] religious beliefs engage both heterosexual and homosexual practices," he said. "[Their] religious beliefs might be considered outdated, or uneconomic for those operating a private hotel, or both, but it is respectfully submitted that, in the particular circumstances of the case, [the Bulls] are entitled to manifest them."

He said if the Bulls were forced to offer double beds to unmarried couples they would "have to stop operating".

Robin Allen QC, for Mr Hall and Mr Preddy, told judges that Mr Hall and Mr Preddy had a "lawful civil partnership" and the guest house should have been "open" to them in the same way it was to heterosexual married couples. He said the Bulls were "missing the point" and argued that Judge Rutherford had taken a "correct approach".

The two-day hearing continues and is expected to end with a reserved judgment.