David Cameron is due to give his keynote speech on Sunday
The Conservatives will contest the general election on six themes, the party has announced at its spring conference in Brighton.
They cover the national debt, the economy, family, the NHS, schools and changes in Westminster.
David Cameron dismissed criticism that the Tories were too "timid" in a video post on his WebCameron blog, saying their plans were "bold and radical".
Labour's Douglas Alexander said the proposals were "reckless".
The Tories have revealed their election slogan will be "Vote for change".
In his blog, Mr Cameron, said: "The Conservative Party is a modern party and it's a bold, radical party - and that's the way it's going to stay."
He said Gordon Brown was taking the country in the "wrong direction" and Britain was "crying out" for the Conservative Party to bring "[their] values, ideas and energy" and make "big changes".
"I defy anyone to look at our plans and call them timid - because the truth is they cannot be timid if we're to confront and defeat these problems," he said.
Shadow chancellor George Osborne told the conference he wanted to create the "solid economic foundations of a Britain that works for all".
He said: "Our country stands at one of those forks we come across as we travel the roads of our history," adding that the public had to make a choice.
"Britain can either continue down a path of decline and fall, a path with rising debts, higher mortgage rates, ever rising taxes and high unemployment.
CONSERVATIVE ELECTION THEMES
Act now on debt to get the economy moving
Get Britain working by boosting enterprise
Make Britain the most family-friendly country in Europe
Back the NHS
Raise standards in schools
"That is Labour's path. It always has been. We know where it leads and we must never allow this country to be dragged there once again.
"Or we can change direction - tell the difficult truths, put debt and taxes back on a downwards trajectory, and create the solid economic foundations of a Britain that works for all. That is the Conservative path."
Opening the conference, shadow foreign secretary William Hague railed against the Prime Minister, saying Gordon Brown would have to be "dragged kicking and screaming" into the coming general election.
"He may not want to discuss his pension-destroying, gold-selling, golden-rule-breaking, national debt-doubling, money-wasting, tax-raising, colleague-rubbishing, pledge-betraying, election-bottling record, but we do - you can be sure of that," he said.
Labour are using the Conservative conference, which coincides with a Welsh Labour Party conference in Swansea, as an opportunity to launch a new poster attacking Mr Osborne.
The election must be held by June but is expected to take place on 6 May. Recent polls have suggested the Conservative lead over Labour may be narrowing.
Mr Alexander, who is Labour's election co-ordinator, criticised Conservative plans, saying they offered the "wrong kind of change" - and one people "really can't afford".
"From George Osborne's reckless economic plans to their proposals to scrap our cancer guarantees and remove vital support from families, the Tories' proposals would hit millions of people across Britain hard," he said.
BBC political correspondent Carole Walker said Conservatives that had been concerned about a "slide in the polls and recent slip-ups" were hoping a "sharper message" would help them "take the attack to their political opponents".
Mr Cameron would be hoping to recreate the "mood of excitement and momentum he created when he became party leader", she said.
His speech is likely to set out the extent of the economic challenges facing the next government.
Revised figures published on Friday confirmed that the UK did emerge from recession slightly stronger than initially thought but all parties agree the recovery is still fragile.
The Conservatives also unveiled Professor David Kerr, a leading cancer specialist, as the party's new health adviser.
Prof Kerr was once a prominent supporter of Tony Blair and Labour's health reforms but said on Friday that he believed the Tories were now best placed to take the NHS forward.
The Tory conference comes a week after the prime minister revealed Labour's election slogan of "a future fair for all".
Labour is also releasing an image of Mr Osborne, accompanied by the slogan "Chancer not Chancellor".
The Liberal Democrats say only they offer a change to the existing way of conducting politics.
Danny Alexander, the Liberal Democrat leader's chief of staff, said: "It's between the old way of doing politics and the real change represented by the Liberal Democrats".