The Tories have more than doubled their opinion poll lead over Labour in the last month, according to new research.
David Cameron's party is up two points to 38% while Labour tumbles three to 30% - a four-month low in the main national polls, according to the Populus research for The Times newspaper.
The gap would widen to 13% (42% to 29%) if the next General Election pits Mr Cameron against Gordon Brown, as expected.
But the Conservatives would do better still if Environment Secretary David Miliband was to launch a successful Labour leadership bid, the poll suggests.
Most Labour voters (55%) would prefer the Chancellor to take charge rather than a young pretender.
The Liberal Democrats are on 18% - down a point in a poll conducted while the party was holding its spring conference in Harrogate.
Populus surveyed a random sample of 1,509 voters by telephone between March 2 and 4.
