Labour has posted a 12-point opinion poll lead over the Tories - its widest margin of advantage in a ComRes survey for more than seven years.
The Opposition gained two points to 43% on a month ago and the Conservatives dropped two to 31%, in the poll conducted for the Independent on Sunday and Sunday Mirror.
It showed the Liberal Democrats static on 10% and Ukip down one on 8%.
More top news
The UK is facing "sharper disparities" in inequality despite wider global growth, but monetary policy is not to blame, Mark Carney has said.
A plan to secure the future of Port Talbot steelworks will be unveiled to staff on Wednesday, ITV News understands.
The 54-year-old, who has been in office since April 2014, will stand down from his role as Prime Minister to focus on his campaign.