Britain's Conservatives lead the Labour government by 12 points in key seats which they must win to clinch the election, the Daily Telegraph reported on Thursday, according to Reuters. That would be enough to make the Conservatives the largest party after an election on May 6 but not enough to give it an overall majority, an academic said. The paper put the Conservatives on 43 percent of the vote, Labour on 31 percent and the Liberal Democrats on 20 percent in a survey of 100 marginal seats. These are seats where the Conservative vote was just a little behind Labour or the Lib Dems at the last election in 2005. The Conservatives need to win 117 seats from other parties to secure a majority of just one seat in a parliament which will have 650 seats. The poll, by researchers Crosby/Textor, found the Conservatives ahead in 74 of the 80 seats in the survey held by Labour, but behind in all 20 of the marginal seats held by the Liberal Democrats. The paper said the survey showed the Conservatives were on course for a convincing election victory. However, John Curtice, politics professor at the University of Strathclyde, told Reuters the Conservatives needed to be winning marginal Lib Dem seats to be confident of a majority. "Almost undoubtedly this poll is saying to us that probably the Tories would be short of an overall majority," Curtice said.