As Gordon Brown formally announced the dissolution of parliament, the Prime Minister claimed that the Conservatives could not be trusted with the economy.
However, David Cameron said the public had a choice between a “fresh start” under his leadership, offering the country a vision of “hope and optimism” rather than five more years under Mr Brown.
The contrasting tone of the party leaders’ messages was used by George Osborne, the shadow chancellor, to set the scene for the fight ahead in the closest election campaign for almost 20 years. “Britain wants change but it’s going to be a big, hard-fought election,” said Mr Osborne.
“The battle is going to be between hope and fear – hope that the change that the Conservatives can bring can get our economy off its back and the fear of a Labour Government that will throw all sorts of scare stories at us.”
Mr Brown visited the Queen at Buckingham Palace on Tuesday to ask her to dissolve parliament with an election to be held on May 6.
Calling the poll the “most important election for a generation”, Mr Cameron broke with convention by making his opening election speech minutes before Mr Brown had formally announced the start of the campaign.
The Tory leader said: “If you vote Conservative, you are voting for hope, you are voting for optimism, you are voting for change, you are voting for the fresh start this country — our country — so badly needs.”
Mr Brown, who had pointedly assembled his Cabinet colleagues behind him outside No 10, then made his plea for Labour to be given an historic fourth term. In what will be seen as an acknowledgement of his unpopularity with voters, he said: “I am not a team of one.”
The Prime Minister, who is leading his party into an election for the first time, said: “Britain is on the road to recovery and nothing we do should put that recovery at risk.
“We will not allow 13 years of investment and reform in our public services, to build up the future of these great services, to be put at risk.”
Mr Brown recalled the action he had taken to tackle the financial crisis in 2008, suggesting that the Tories could not be trusted in a similar situation. “There will be many big challenges and many big decisions to make over the next few months upon which our future success depends,” he said.
Mr Brown also boasted about his “ordinary middle-class” background, a remark that will undoubtedly be seen as an attack on Mr Cameron’s “privileged” background. “I will never forget the values — doing the right thing, doing your duty, taking responsibility, working hard — that my parents instilled in me,” he said.
Nick Clegg, the leader of the Liberal Democrats, said the election would not be a “two-horse race” and his party had a genuine chance of significantly influencing the outcome.
Immediately after their speeches, Mr Brown, Mr Cameron and Mr Clegg set out on the campaign trail.
The Prime Minister visited Kent and Essex, while the Tory leader met volunteers in Birmingham and Leeds.
Mr Cameron, 43, declared himself “daunted yet excited” by the start of the campaign. He is aware of the scale of the challenge facing him if he wants to become the first Tory Prime Minister since John Major and the youngest premier since Lord Liverpool in 1812.
To win a majority, the Conservatives have to achieve the biggest electoral swing in the party’s history, 6.9 per cent. Overall, they have to win an extra 117 seats. However, the party has been buoyed by the impact of their pledge to reverse Labour’s planned rise in National Insurance contributions and is preparing to release a new list of leading businessmen backing the policy.
Among them will be Bob Wigley, a former banker who has written a review of the City’s competitiveness for Boris Johnson, the Mayor of London; Tim Steiner, the chief executive of Ocado and Nick Robertson, the founder of the online fashion retailer Asos.com.
In a speech to party supporters in Leeds last night, Mr Cameron warned that Labour would fight on its experience of government. “We all experienced their experience,” he said. “We were there when they doubled the national debt, when they brought in 178 tax rises, we were there for record youth unemployment. We were there when they sold the gold.
“We shouldn’t have to put up with what we’ve got. Britain deserves so much better than what we’ve got today.”
Today, the three party leaders will clash in a final Prime Minister’s Questions session in the Commons before Parliament is dissolved next Monday and the election campaign begins in earnest.