The Conservative co-chairman, Grant Schapps, has cast doubt on reports in two newspapers that a senior Tory aide described party activists as "mad, swivel-eyed loons".
Asked who was behind the alleged comments, he told Channel 4:
Unfortunately I can't reveal the answer to that, simply because I was not there and as far as we are aware it was not even said, but we just don't know.
I don't believe anyone senior would say this type of thing, it's not an attitude or a view I have ever heard expressed in No 10, in Central Office. We respect and work with people who work incredibly hard as volunteers, unpaid, for the party.
I'm trying to make clear, I don't believe it's ever been said. You can always run a story that said there were 250 people in a room and one of them said this.
The trouble is with this story we don't know who is supposed to have said it.
David Cameron sent an email to members of his Conservative Party urging unity.
The Tory grandee Lord Howe has accused the Prime Minister of 'losing control' of his party as divisions over Europe come to the fore.
The Conservative Party has moved to head off a row with grassroots activists after a Tory ally reportedly described them as "loons".