Green Party membership has rocketed by 100% in the year to December as former Labour, Liberal Democrats and Conservatives turn to the environmentalist organisation in England and Wales.
The so called "Green surge" has seen the party, which was found in 1973, double its membership in 11 months.
The party now has more than 27,618 members after a jump of 500 people signing up over the weekend.
"This is a real landmark in the 'Green surge'. To have doubled the membership of the party in less than a year is a real marker of the way in which people in England and Wales are seeing that we need real change in our society, not the business-as-usual politics offered by the three largest parties," said Natalie Bennett, the leader of the Greens.
"Talking to new members around the country, their reasons, and the trajectories that brought them to the Green Party, vary a great deal.
"There are many former Labour and Liberal Democrat members who are fed up with parties that are happy to see society continued to be run for the benefit of the 1% and the continued trashing of our natural environment.
"Others are former non-voters, who see that to create the rapid change we need we need a new kind of politics.
"Some are former Tories, horrified by the government's fracking fantasy or worried by its failure to tackle our fraud-ridden, corrupt, reckless financial sector."
But the data, which comes before the 2015 General Election next may, means that the Greens are still well behind Labour and the Conservatives in terms of membership numbers.
The most recent publicly available figures put Labour on 190,000, the Conservatives on 134,000, the Liberal Democrats on 43,451 and Ukip on 39,000 members.
The latest poll from YouGov for The Sun put Labour and the Conservatives neck-and-neck on 32%, with Ukip on 15%, the Liberal Democrats on 8% and the Greens on 6%.