An activist who was part of David Cameron's 2005 leadership campaign has become the latest to criticise the Conservative party leader.
David Cameron was under fire for his decision to visit Rwanda
Speaking to the BBC, Ali Miraj said Mr Cameron used "gimmickry" and was "obsessed with PR".
The criticism came as Mr Cameron prepares to outline Tory plans for improving discipline in schools.
In addition, two polls in Tuesday's press suggested a "Brown bounce" as Labour kept ahead of the Conservatives.
Mr Cameron is to suggest a policy which would see the creation of contracts between schools and parents that could be enforceable.
He wants to change the system under which families can appeal against their children being excluded.
Mr Miraj, who was among David Cameron's strongest supporters, also questioned his selection of Tony Lit as Tory candidate in the recent Ealing Southall by-election.
He said: "I'm disillusioned because I think substance has been replaced by PR.
"What I'm asking for is some substance and some credibility and not box-ticking and gimmickry.
"People have had enough of Tony Blair for 10 years. They don't want another Tony Blair.
"The contrast is with Gordon Brown. David Cameron in my view has got substance, somewhere in there, but I'm afraid that in recent weeks, that has been taken over by PR.
"What I want to see is that balance redressed so that we can have a decent chance of winning the next election and if present form continues, we certainly won't."
Mr Miraj, who is on the board of two of the party's policy review groups, questioned the decision to pick Mr Lit as a Tory candidate when the businessman had only joined the party days earlier.
In the by-election in Ealing Southall, Mr Lit ended in third place.
Mr Miraj also questioned Mr Cameron's judgement over his decision to visit Rwanda to learn about development issues while parts of his Oxfordshire constituency suffered flooding.
Mr Miraj is hoping to be selected as a parliamentary candidate himself.
Also on Monday, former party chairman Lord Saatchi warned "nicey-nicey" politics would not win the next election.
Lord Saatchi criticised David Cameron's focus on branding and urged him to appeal to voters on the economy.
Writing in London's Evening Standard newspaper, Lord Saatchi said the Tories needed to find "an expression of true Conservative ideology".
He pointed to Tony Blair's reforms of Labour in the 1990s which led to the party developing a reputation for economic competence.
"The earth shook," he said.
"When the Conservative Party moves along the dimension from nasty to nice, nothing happens.
"It follows that nothing will happen until the Conservative Party has something compelling to say about the subject that matters - economics."
Two polls by national newspapers brought more bad news for Mr Cameron.
A survey for the Times put the Labour party six points clear of the Conservatives with 39% of the vote compared to 33%.
The Populus poll, which questioned 1,511 adults, also found Mr Cameron was personally lagging behind Prime Minister Gordon Brown in the popularity stakes.
More than half of those surveyed (56%) believe Mr Brown has what it takes to be a good prime minister, compared with 32% for Mr Cameron.
A further poll for The Independent put Labour on 37% (up five points on a similar poll last month) and the Conservatives on 34% (down three).
The CommunicateResearch survey of 1,006 adults suggested the swing to Labour since Mr Brown became prime minister last month has come largely from male voters.
Mr Cameron had also been criticised earlier by ex-Tory frontbencher Graham Brady for failing to reach out to voters in the north and Midlands.
Mr Brady said the Conservative leader was not making sufficient headway in the key battlegrounds which will decide the next general election.
Mr Brady, who quit as shadow Europe minister over the grammar schools row, said Mr Cameron's appeal was limited to urban liberal circles around London.