Labour has slumped to 25% in a new poll, trailing 18 points behind the Conservatives on 43%.
Support for Jeremy Corbyn's party equalled the lowest level it has ever reached in a series of ICM polls for The Guardian dating back to 1983, though it has dropped as low as 24% in other recent surveys by mainstream pollsters.
The party previously hit 25% in the ICM series in June and August 2009, when Gordon Brown was at the depths of his unpopularity as prime minister following the financial crash, said ICM director Martin Boon.
Labour dropped one percentage point compared to a similar poll two weeks ago, while the Conservatives fell two points.
Benefiting were the Liberal Democrats, up two points on 11% and Ukip, up a single point on 11%. The Greens were unchanged on 4%.
:: ICM Unlimited interviewed 2,005 adults from March 31 to April 2.