"To abandon deficit reduction now would throw away all the progress we have made," Cameron told Conservatives gathered in Manchester, northwest England.
His speech was the climax of the political conference season, which has seen all Britain's main parties rally the faithful and appeal to voters ahead of a national election 18 months from now. Cameron's Tories currently govern in coalition with the centrist Liberal Democrats, but hope to win a majority government in 2015.
Opinion polls consistently put the opposition Labour Party ahead of the Conservatives, though the margin is so small that no party can be confident of victory.
In a keynote address that was more about broad vision than concrete policy proposals, Cameron reeled off great British achievements from the Magna Carta to the government of Margaret Thatcher.
He said his party "is on the side of hardworking people," promising to cut taxes and red tape and unleash the power of economic innovation.
"Profit, wealth creation, tax cuts, enterprise are not dirty, elitist words," Cameron said. "They're not the problem, they really are the solution."
Cameron, 46, strode confidently onstage to a song by The Killers, but his speech revealed a prime minister at pains to fend off attacks from both left and right.
Labour paints the Tories as a party of the rich, and depicts Cameron a millionaire educated at the elite Eton school and Oxford University as out-of-touch. Cameron did nothing to undermine that view this week when he fell into the classic political trap of not knowing the price of a loaf of inexpensive white bread.
"I don't buy the value stuff," Cameron said on LBC Radio. "I have a bread-maker at home."
Many on the Conservatives' traditionalist wing are also wary of Cameron's privileged metropolitan image and liberal attitude on issues such as same-sex marriage, which Britain recently legalized.
The right-wing United Kingdom Independence Party, or UKIP, is winning support away from the Tories with attacks on the European Union, mass immigration and a perceived culture of political correctness.
In his speech, Cameron disparaged Labour as a party of "1970s-style socialism" whose big spending when in office between 1997 and 2010 had caused the current deficit.
And he appealed to the Conservative grassroots, promising to toughen up immigration and welfare rules and give voters an "in or out" referendum on EU membership. The party has also promised a tax break for married couples, an example of the kind of low-cost sweetener it will rely on to attract voters without increasing spending.
Cameron was cheered by Tory delegates, but UKIP leader Nigel Farage called the speech "an abysmal damp squib."
Labour leader Ed Miliband tweeted: "The last thing families want is him to 'finish the job' when prices have risen faster than wages and average pay is down by almost 1,500 pounds ($2,400)."
Miliband will likely be Cameron's election opponent, but the prime minister's biggest rival lurks within the Conservative Party. The country's most popular Conservative politician is not Cameron but Boris Johnson, the tousle-headed, Latin-spouting mayor of London. Johnson's rivalry with Cameron stretches back to their days at Eton, and the mayor has spoken of his desire to be prime minister.
Johnson will end his second term as mayor in 2016 and is expected to return to national politics. Cameron said this week with no obvious sign of gritted teeth that he would welcome Johnson back to Parliament.
In a conference speech, Johnson referred to his own ambitions in his usual style with a laugh that masks seriousness.
He recalled meeting former French Prime Minister Alain Juppe, who was premier and a city mayor at the same time.
"That's the kind of thing they do in France a very good idea in my view," Johnson said. There was a moment's pause before he shouted "Joke!"
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Jill Lawless can be reached at http://Twitter.com/JillLawless
