The Conservatives are launching a £500,000 advertising campaign to recruit online "friends" of the party.
The green message is one of ten being promoted by the Tories
In an echo of Radiohead's recent album launch, there will be no fixed charge for becoming a Conservative supporter on Facebook, MySpace, iVillage or Bebo.
"People can pay as little or as much as they want to," said shadow chancellor George Osborne in what he said was a groundbreaking move in UK politics.
Labour and the Lib Dems already allow people to register as e-supporters.
Under the Labour Supporters Network, people can sign up for online bulletins without joining the party, while the Lib Dems have an e-supporters scheme for people "not ready" to join the party.
The Lib Dems have also had their own Facebook page for the past year and claim that "about a third" of their new members are now recruited online.
The Conservatives are launching their own page on social networking sites Facebook, MySpace, Bebo and iVillage.
Friends will then be sent regular updates on party activity and invitations to take part in social action projects in their area - but they will not be able to vote in leadership elections or any of the other activities open to a full party member.
Mr Osborne said the aim was to "broaden the base" of the Conservative Party, which in line with other major parties has struggled to increase its membership in recent years.
He said the Conservative campaign was inspired by the race for the US presidential nominations, which has seen candidates such as Barack Obama raise millions of dollars through donations from individual web users.
"We want to be the groundbreakers in British politics," said Mr Osborne.
He said the party was also impressed by the rock group Radiohead, who launched their most recent album, In Rainbows, via an online honesty box, which allowed fans to pay what they thought the music was worth.
The recruitment drive will be supported by a £500,000 advertising campaign in national and local newspapers and a short film by Matthew Vaughn, who directed British gangster film Layer Cake.
In the film, which will be used as a party political broadcast at May's local elections, Conservative leader David Cameron sets out 10 key areas in where he says the Tories can make a difference and deliver "real change".
These include traditional Conservative policies such immigration and crime, but also the environment, education and the NHS.
The theme music for the campaign is Jimmy Cliff's You Can Get It If You Really Want It, which is also its slogan.
Mr Osborne said it was a "big decision" by the party to launch a major advertising campaign so far from a potential general election but it showed the "confidence" the party had in its message.
But Lib Dem internet campaigns chief Mark Pack said the Conservatives were trailing behind them when it came to online recruitment of members.
"We have found it to be a very effective way of reaching out to a wider audience," he told BBC News.
Labour also claims to have pioneered the use of the internet to recruit supporters.