The Guardian/ICM poll put the Conservatives on 36 percent, up six points from last month, and at its highest level in that polling series since May 2012. Backing for the opposition Labour party fell one point to 32 percent.
Most other opinion polls since the start of the year have had Labour narrowly ahead or level with the Conservatives before what is shaping up to be one of the most unpredictable elections in modern British history.
Monday's Guardian/ICM poll of 1000 adults showed support for the anti-EU UK Independence Party (UKIP) and the Green Party fell two points each to 9 percent and 7 percent respectively, while Cameron's junior coalition partners, the Liberal Democrats, dropped one point to 10 percent.
An Ipsos MORI poll last week also showed the Conservatives and Labour were picking up support at the expense of their smaller rivals.
In a sign of how uncertain the outcome of the May 7 vote remains, a Populus poll also published on Monday put Labour ahead on 33 percent, compared to 31 percent for the Conservatives.
