Party reaches crucial figure of 40 per cent for first time since mid-February.
Voters also expect David Cameron to perform best in the leaders' debates.
Latest figures would leave Labour as the largest single party.
Tory lead recovers but hung parliament is still likely.
Tory lead cut to just two points in new YouGov poll.
Latest Ipsos MORI poll puts Tory lead at lowest level since December 2008.
YouGov poll for the Sunday Times (21 February) reveals narrowest Tory lead since 2008.
Conservatives on track for a small majority as party rises two points.
Tory lead rises to 12 per cent in first poll since leadership crisis
Back in hung parliament territory
New survey shows Tory lead narrowing to 10 points
Poll finds 57 per cent oppose independence as Salmond prepares to publish referendum plans
Party boosted by public sympathy for Brown over Sun attacks
Conservatives lead Labour by 10 points but would win a majority of only two
Figures would give Conservatives a Commons majority of 106
Party on track for a majority of 58 at the next election as voters back Cameron's anti-statism
Conservative lead cut to 11 per cent as Labour rises three points
Party boosted by the conference season but support for Cameron's leadership rises
Tories also lead Labour on every policy issue except the NHS
First poll since David Cameron's conference speech shows party's lead rising by 8 per cent
Party halves the Tory lead to seven points on the back of its conference
Poll also shows that a majority of voters remain unsure that there is "substance" behind David Camer
Party on track for a majority of 96 seats at the next election
Tories seventeen points ahead of Labour in new poll and on track for majority of 110
Party just a point ahead of the Liberal Democrats in the latest ComRes poll
Party up two points to 41 per cent in new ICM poll with Labour unchanged on 27 per cent
Favourite to succeed Brown would leave the Tories six seats short of a majority
Tories down 10 points to 30 per cent in ComRes poll
Party tied with Liberal Democrats on 18 per cent