David Cameron urged restive Tories to focus their energies on fighting Labour as he sought to quell unrest among activists over his leadership.
He used a speech to the party's spring conference to insist he was sticking to traditional Tory values after a turbulent fortnight of internal division.
He faces warnings from a new Tory group meeting at the conference that the party faces a "severe defeat" in 2015 if he fails to "reconnect" with party members and abandon gay marriage laws over which they have quit "in droves".
Mr Cameron did not address the issue directly in his speech to the London gathering - which he used to insist he was engaged in fighting for an "aspiration nation" in line with the traditional party icons Margaret Thatcher and Winston Churchill.
But he fired a warning shot that with less than 1,000 days until the next general election, the party had " a real fight on our hands" and must concentrate on the real enemy.
"Anyone in this party who's in any doubt who we should be fighting, what we should be debating, where our energies should be focused, I tell you: our battle is with Labour," he declared.
"Let's not mince our words: this is a bunch of self satisfied, Labour socialists who think they can spend your money better than you can, make decisions better than you can and tell you what to do and we should never, ever let that lot near government again.
"That's who we're fighting against.
"And we know who we're fighting for: for all those who work hard and want to get on."
He concluded: "Does this party ever shy away from the fight? No.
"I'm up for it. This party's up for it. So let's give it everything - I mean everything - we've got."
Mr Cameron warned his party that the government's task was not going to get any easier as it battled to revive the UK economy - despite successes in key areas such as schools, welfare reform and job creation.
"We always knew we'd face pretty big challenges right now," he said.
"It's mid-term. We're wrestling with historic debts.
"Recovering from the deepest recession since records began.
"Fixing a broken welfare system and education system - and yes, a broken society too.
"Anyone who thought it was going to be easy - they're wrong. Anyone who thinks it's going to get easier - they're wrong too.
"But let's remember - above all the background noise - what this is all about: "The national interest: first, last, always. This is a battle for Britain's future we are engaged in.
"So let the message go out from this hall and this party: we are here to fight; we are here to win; and we have never been more up for the task of turning our country around."
Mr Cameron said his party gave people the "tools to succeed" - and ensured the "ladders" were there for people to get on no matter what their background.
"Great Conservatives down the generations have put those ladders in place.
"When Churchill invented the labour exchanges that helped people into work.
"When Macmillan built new homes.
"When Thatcher fired up enterprise so people could start their own businesses.
"That's what we're doing in the Conservative Party right now."
He focused a large part of his speech on help for young people - including a newly-announced boost to primary school sports.
The premier, who has faced backbench criticism for what some dub a "posh, white, male" inner circle, said: "My dream for Britain is that opportunity is not an accident of birth, but a birth-right."
He said he wanted the education system to be "like the pushiest, most sharp-elbowed, ambitious parent there is", adding that he was proud that he and his wife were "pushy" for their own children.
"I say it loud and proud: Samantha and I are pushy parents."