Labour has opened a three-point lead over the Conservatives in the most decisive poll movement since the general election campaign kicked off in earnest.
On the day Ed Miliband put cutting the deficit at the heart of Labour's election manifesto, a YouGov poll for The Sun put his party on 36% and the Tories at 33%.
It is the largest lead the pollster has given either party since the dissolution of parliament on 30 March and suggests Labour's campaign is gathering momentum ahead of the election.
The survey, which questioned 1,717 adults, was conducted between 11 and 12 April when Labour and the Tories announced policies they hoped would sway undecided voters.
The Conservative Party claims it would use money from an expanding economy to pay for the £8bn ($12bn) shortfall in NHS funding predicted by 2020 and would abolish inheritance tax on homes valued up to £1m.
Meanwhile, Labour said it would raise an extra £7.5bn a year through closing tax loopholes and reintroduce the 50p top rate income tax.
The poll lead comes as Miliband used a speech in Manchester to unveil his party's manifesto. He said a Labour government would not increase borrowing and pledged to reduce the deficit at each budget.
He also vowed to increase the national minimum wage to £8 an hour by October 2019.
The Tories rebuked Miliband's vision, with Treasury minister David Gauke saying it had "no plan to clear the deficit and balance the books".