Rising to his feet at the Hampstead Conservative dinner, veteran Fleet Street journalist Andrew Pierce warned his audience, with some trepidation, that he was about to venture “off message”.

To his surprise, and what could be to the concern of the party leadership, the gathered throng warmed to his scathing criticism of David Cameron’s reform of the party – abandoning his core voters to woo the younger electorate.

Though speculation over looming leadership bids has been widely dismissed by the Westminster lobby, the Daily Mail’s consultant editor and columnist claims rumblings from grassroots supporters are far more troubling for the Prime Minister.

Increasing international aid, a failure to cut taxes and gay marriage are all issues which have contributed to the sense of malaise among the party faithful, says Mr Pierce, whose infatuation with politics started as a cub reporter on the Gloucestershire Echo.

The 52-year-old, who came second at last week’s Press Awards in the Political Journalist of the Year category, said: “There was warm applause and loud claps when I said, ‘Why does he (Cameron) go out of his way to upset people in the party? He goes out of his way to alienate his own supporters’.

“In my experience the Tory Party has been slavishly loyal to the leader, even with Iain Duncan Smith, who was a disaster.

“It’s extraordinary how they have turned on Cameron. I think for some they have never forgiven him for not winning the election against a basket case [former Prime Minister Gordon Brown].”

Though gay himself and in a long-term relationship, Mr Pierce, who often appears on the newspaper review slot on Sky News, dismissed gay marriage as a “political football” and said he would never consider tying the knot.

“Cameron thinks it will help modernise the party and bring all these new people bouncing into the Tory Party,” said Mr Pierce, who lives in Belsize Park.

“It’s a gamble that has not paid off and has caused untold damage. There are far more important things for this government to be doing.”

Part of the damage he fears will be felt by Simon Marcus, the Conservative candidate for the Hampstead and Kilburn Parliamentary seat.

Mr Pierce, who has never belonged to a political party, said: “Why did the former Conservative candidate Chris Philp walk away from the seat? I don’t want to talk down Simon’s chances but the fact that he did walk away speaks volumes about Chris’s mindset.

“Chris is clearly looking for a safer seat.

“Simon really has to play the local boy card, but I’ll expect Labour to pick someone local too. I think it’s going to be a heroic struggle and it will come down to who wins the Lib Dem votes.”