Prime Minister David Cameron has denied he has ever ridden the horse which was lent by police to former News of the World editor Rebekah Brooks.
But he confirmed that he had ridden as leader of the Opposition with Mrs Brooks's racehorse trainer husband Charlie, a friend since they went to school at Eton.
It emerged earlier this week that the Metropolitan Police lent a horse called Raisa to Mrs Brooks, who resigned last year as chief executive of News International amid the furore over phone hacking allegations.
The horse was stabled at the former tabloid editor's Cotswolds home from 2008-10 before being handed back to the Met. It is understood that the animal has since died.
In an interview with Channel 5 News, Mr Cameron was asked whether he had ever ridden Raisa.
He said: "It's a matter of record that I have been riding with Rebekah Brooks's husband, Charlie Brooks.
"He is a friend of mine for 30 years standing and a neighbour in my constituency so that's a matter of record.
"But since I have been Prime Minister I think I have been on a horse once and it wasn't that one."
A Downing Street spokeswoman said she was not aware of which horse Mr Cameron was referring to.