Without naming his rival, David Davis, he warned that if the party fought another campaign based on shoring up its core vote - the strategy they followed this year and in 2001 - they would be handing victory to Gordon Brown.
The previous day, Mr Davis had told Tory women that the Conservatives did not need to " reinvent ourselves" to win an election. But in a speech last night to London Tories, Mr Cameron said: " Our party faces a clear choice in this leadership contest. Do we move to the right, or do we fight for the centre ground? Do we stick to our core vote comfort zone or do we reach out? Do we repeat the mistakes of the past, or do we change to win for the future?
" That is our choice. If we get it right we can end the Blair era. If we get it wrong, the Blair era stays - under new mis-management: more spin, more headline-chasing, more bureaucracy, more centralisation, more spending, more borrowing, more waste, less reform, higher taxes - from Gordon Brown."
The speech was his most direct attack on his rival, and a sign that the strain of a long leadership is causing tempers to fray. Previously, each candidate had avoided suggested that the other was incapable of leading the Tories to victory.
But Cameron's supporters were irritated by a rumour which they claimed was being put about by the Davis camp, that their candidate was frightened of facing difficult interviews on television. Last night, Mr Davis put himself through an interrogation by Newsnight's feared interviewer, Jeremy Paxman - something Mr Cameron has not yet done.
Mr Paxman asked why the Tories should want to be led by someone described as a " thug, a bully, an adventurer, disloyal, congenitally treacherous and winner of the whips office shit of the year" . Mr Davis replied: " What you are getting there is a view from a small group, I stress a small group."
Davis supporters suggested that Mr Cameron was ducking tough interviews at a time when party members are receiving their ballot papers through the post, but his camp vehemently deny the accusation and saying that the delay is attributable only to a problem with agreeing a date.
Mr Cameron also rubbished his rival's tax plans yesterday. Mr Davis has proposed to cut taxes by £38bn over five years. Yesterday, he had said that he would go ahead even if there was an economic slump, funding the cuts by borrowing.
" If you are in a slump, what you don't do is increase taxes," he said on BBC Radio Five Live. " It becomes a different formula from what I talked about before. But what you don't do is increase taxes because that makes the slump worse - you are taking spending power out of the economy. What you do actually is you reduce taxes. You have to borrow at that point. You can't afford to do it any other way."
But Mr Cameron countered: " The trouble with David's plan is that he is saying five years in advance that he is going to cut taxes by £38bn. I think he is saying it whether the economy is growing or shrinking. And I don't think that's right. What people want to know is that the Conservative Party is going to be prudent and sensible and moderate and reasonable and trusted with running the British economy."Reuse content