The opposition Conservatives are calling it the most important election in decades.
David Cameron told his supporters he was delighted the race is finally on, vowing to travel the country to talk and listen to people.
Cameron said: “It’s about the future or our economy. It’s about the future of our society. It’s about the future of our country. It’s the most important general election for a generation.”
But with a hung parliament thought to be a strong possibility, the Liberal Democrats, led by Nick Clegg, are seen as potential kingmakers in any new government.
Clegg said: “The real choice is between the old politics of Labour and the Conservatives and something different, something new, and that’s what we offer. We’ve got to do something new this time.”
One new opinion poll suggests that Labour could remain the largest party in parliament but still be 30 seats short of a workable majority.
However, two other surveys show a Conservative lead over Labour, extending into double digits.