Lord Feldman said it was “completely untrue” that he made the remarks, which several newspapers reported yesterday as being made by an unnamed member of Cameron’s inner circle.
A Downing Street spokesman said: “The Prime Minister supports Lord Feldman’s position.”
The spokesman added: “It is categorically untrue that anyone in Downing Street made the comments about the Conservative Party Associations and activists reported in the Times and the Telegraph.”
Reports claimed a senior ally of Cameron made the comments accusing MPs of being forced to take hardline views on issues such as Europe because of pressure from their local associations.
The senior figure reportedly said: “There’s really no problem. The MPs just have to do it because the associations tell them to, and the associations are all mad swivel-eyed loons.”
The comments were made at a private dinner by a figure with “strong social connections” to the Prime Minister, the newspapers reported.
In a statement Lord Feldman, a friend of Cameron’s from Oxford University, said: “There is speculation on the internet and on Twitter that the senior Conservative Party figure claimed to have made derogatory comments by the Times and the Telegraph is me.
“This is completely untrue. I would like to make it quite clear that I did not nor have ever described our associations in this way or in any similar manner. Nor do these alleged comments represent my view of our activists.
“On the contrary, in the last eight years of working for the party, I have found them to be hard working, committed and reasonable people. They are without question the backbone of the party.
“I am very disappointed by the behaviour of the journalists involved, who have allowed rumour and innuendo to take hold by not putting these allegations to me before publication. I am taking legal advice.”
The reported remarks came after 114 Tories, plus two Conservative tellers, expressed “regret” that the government’s legislative programme did not contain a bill paving the way for the in/out referendum on EU membership before 2017 promised by Cameron.
Tory Peter Bone, one of the sponsors of the amendment to the Queen’s Speech, said if the reports were correct “anyone who takes these views could not possibly want to remain a member of the Conservative Party, even less still want to advise the Prime Minister”.
Former minister Tim Loughton said if the reports about the unidentified person were correct Mr Cameron should “show some leadership and sack him”.
Tory MP Tracey Crouch wrote on Twitter: “I wonder if this ‘aide’ has ever been a member of an association, delivered a single leaflet, packed an envelope or knocked on a door? My activists are far from being ‘swivel eyed loons’. They are hard working people who care passionately about local area & future of country.”
Nadine Dorries, who has criticised the “chumocracy” of old friends surrounding Cameron and has floated the idea of standing as a joint Conservative-Ukip candidate at the next election, wrote: “If an MP described activists as mad swivel eyed loons they would be all over the Media. Why don’t we know the name of the No 10 aide?”
Relations between the party leadership and grassroots traditionalists have been strained by Cameron’s support for gay marriage and over the thorny issue of Europe.
Ukip leader Nigel Farage, who was forced to flee a pub in Edinburgh last week after an anti-Ukip protest, wrote on Twitter: “If you are a Conservative supporter who believes in Ukip ideas then your party hates you. Come and join us.”
Last night Tory co-chairman Grant Shapps compared the row to the “plebgate” stories surrounding former chief whip Andrew Mitchell and allegations against peer Lord McAlpine which have resulted in libel claims. Shapps said: “I know Andrew [Feldman], he is a very decent guy, I believe him, he is telling the truth, and that for me is that.”