David Cameron has put "presentation before principle" in his quest for votes, one of his former advisers has said.

George Bridges, the Conservative Party campaign director's during the 2010 election campaign , has slammed the prime minister's obsession with "decontaminating" the Tory brand at the expense of promoting of core Conservative beliefs such as cutting taxes.

"Just as Heinz may change the level of salt, the label or the price of a can of baked beans, political parties began to ditch or adopt policies to suit the public taste, day by day, week by week," he said.

Writing in the Daily Telegraph today, Bridges said politicians who are guided only by the polls rather than their conviction are engaged in a "forlorn search for popularity".

"They are not selling baked beans, but something more complex: vision, belief and leadership. And the more politicians change to reflect every passing fad, the less the public believes what they say, and will-o’-the-wisp flits away," he said.

Bridge's criticism can be read as an attack not just on Cameron, but on George Osborne. The chancellor is often credited as the driving force behind the modernisation project including the Tories' pre-election pledge to match Labour’s public spending commitments and his advocacy of socially-liberal policies including, in a recent column for the Times, gay marriage.

In his own Telegraph article, Bridges issued a "mea culpa" for failing to speak up against Cameron and Osborne's modernisation strategy. "I sat there as the culture of politics changed. And I did nothing," he said.

"The mindset of political strategy is now poisoning the well of politics. Those politicians who do have the guts to highlight unpalatable truths, and what they would do about them, are criticised.

"On Europe, politicians are told that voters don’t care about it – so shut up. Meanwhile, politicians talk of taxing 'wealth' more because of what that would 'say' about their party, not whether it is the right or wrong thing to do."

However Tim Bale is professor of politics at Queen Mary, University of London and the author of The Conservative Party from Thatcher to Cameron, said he disagreed with the premise of Bridge's criticism.

"It assumes there was this golden age when this didn't happen, where politicians have never been about strategising," he said.

And he suggested that the critics of the modernisation project were simply unhappy with the policies, not with any perceived lack of conviction on behalf of Cameron and Osborne.

He said: "One person's standing up for principle is another person's betrayal of public opinion."

Bridges' intervention comes after Australian political strategist Lynton Crosby was hired to run the Conservative's 2015 general election campaign.

Crosby helpe Boris Johnson's win re-election as mayor of London in May - but also worked on Michael Howard's failed 'are you thinking what we're thinking' 2005 general election campaign that focused on 'core' Tory issues such as immigration.

His return has concerned card-carrying Tory modernisers who fear he will drag the party away from the centre ground and undermine ongoing efforts to widen it's appeal to floating voters, especially ethnic minorities.

In a stinging "open letter" to Crosby published on the ConservativeHome website, Lord Ashcroft, the
Tory donor who conducts extensive polling in marginal seats, said he had argued against the Australian's appointment.

"To win a majority, we need to attract people who thought about voting Conservative in 2010 but decided against it, not just keep existing Tories on board," Ashcroft said.

Crosby's appointment has also led to speculation that Andrew Cooper, the prime minister's chief pollster and uber-moderniser, could be on his way out of Downing Street.

That should be please George Bridges.