The Conservatives have asked the Electoral Commission and the Information Commissioner's Office to investigate the legality of two tactical voting websites, in what promises to be the first of many skirmishes in cyberspace during the election campaign.

The party's headquarters has complained to the Electoral Commission about StopHague.com, which is targeting the anti-Conservative vote in the marginal Kingston & Surbiton and Wimbledon constituencies, after the website's founders refused to close it down voluntarily.

Meanwhile, Ian Bruce, the Conservative MP for Dorset South, said he had reported Votedorset.net, set up by singer/songwriter Billy Bragg, to the information commissioner. He argued that the site, which is trying to mobilise the anti-conservative vote in South Dorset and West Dorset, "does not comply with data protection act and isn't registered with the Information Commissioner's Office".

The websites, which operate as clearing houses to match tactical voters in marginal constituencies, draw on the experience of those set up to maximise the anti-Republican vote in last year's US presidential election.

The Conservative party said it was waiting for the Electoral Commission to clarify the rules on such sites and would decide on legal action once the position was clear. Threats of legal action forced several of the US sites out of business before polling day.

However, the Electoral Commission said the sites were not illegal, not least because electoral laws have yet to be written for new media, while the ICO said that it did not see any problem with Votedorset.net as it was "unlikely" to be holding or processing personal data.

As the cyber-election gets into full swing, there have also been allegations of underhand tactics from voteswapping sites. Votedorset.net said it had been attacked by a "Tory loving robot" which persistently logged-on and registered on the site, preventing other users accessing it. It also alleged that Conservative activists had bombarded the site with 'spam' mail from bogus addresses.

Mr Bruce said neither he nor his local Conservative party had anything to do with the attacks, although he had repeatedly signed up to the site, collecting "dozens of names" of people who intended to vote tactically.

While the Conservatives are playing down the influence these sites will have on the election, Jason Buckley, founder of Tacticalvoter.net, makes bold claims for his creation. The site has had over 10,000 unique users since its launch and 1,300 pledges, he says, with the election still nearly a month away.

"The US sites only had two weeks, if they had got another two they would have been a different occupant at the White House.

"We are essentially doing for politics what Napster did for music."