The Conservatives currently lead Labour 36% to 30% just 10 days before the general election, according to the latest Lord Ashcroft poll.
The Tories have increased their lead by two points since the previous Ashcroft poll, with Labour remaining on the same figure.
Elsewhere, the Liberal Democrats are down a point at 9%, Ukip slips down two to 11%, the Greens are up three at 7% and the SNP down two at 4%.
The latest results, sourced between 24 to 26 April, now mean the Tories have led in six of the previous eight Ashcroft polls.
Ashcroft notes there has been a notable increase in the number of Labour supporters who said they would prefer to see Ed Miliband become prime minister compared with when the question was last asked in February.
He said: "This will be partly down to potential Labour voters who find him an insurmountable barrier switching to another party, and partly to existing Labour voters thinking Miliband has had a good campaign. I also suspect that some who have decided to vote Labour despite their doubts about its leader are now telling themselves that he might not be so bad after all."
Ashcroft also points out how there has been "little change" in people's perception of David Cameron during the course of the campaign.
He added: "I found just over half of voters saying either that they were satisfied with David Cameron (32%) or that they were dissatisfied but preferred him to Ed Miliband (23%)."