Raisa, the horse at the centre of the equine debacle, was loaned to Brooks in 2008, as part of a scheme which is open to the general public.
An aide to the PM has admitted it is possible that he may have borrowed the horse.
Cameron attended Eton with Charlie Brooks, the former News of the World editor’s husband, and both couples live in the exclusive village of Chipping Norton in the Costwolds, where they are said to regularly ride together.
The source told the Daily Telegraph: “It’s possible. He used a number of Charlie’s horses.”
Cameron denies claims made by the News of the World that he and Brooks went riding together.
Rebekah Brooks was defended by Rupert Murdoch over the incident, referred to on Twitter as Horsegate.
“Now they’re complaining about R Brooks saving a horse from the glue factory,” the media magnate tweeted.
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