The Conservatives have called on the Electoral Commission to investigate a website created to organise tactical voting against the party.

The creator of tacticalvoter.net is calling on voters in key marginal wards to swap their votes over the net to prevent the Conservatives winning. "You have nothing to lose but a Tory MP," the site claims.

Jason Buckley, who says he has no party affiliation, claimed that what he was doing was perfectly legitimate.

"All we are doing is acting as a political dating agency between Labour and Lib Dem voters in marginals. It could be the start of a beautiful relationship, and we could stretch the metaphor to talk about it doing something to the Tories," he said.

People using the 27-year-old businessman's site can swap e-mail addresses to co-ordinate how they vote. Users make an online pledge to vote tactically for whichever party in their constituency is most likely to defeat the Conservative candidate.

The site provoked an angry response from the Conservatives. "The Electoral Commission must look into this to see if it is being run properly. It's not a politically neutral thing and is obvious political engineering. It seems like a desperate attempt by the Lib Dems and Labour to stop the Tory challenge," said a spokesman.