Natalie Bennett was elected the new leader of the Green Party in England and Wales in a ballot of party members on Monday.
The 46-year-old chair of Green Party Women and Camden Green Party will replace MP Caroline Lucas as the party's leader, beating three candidates.
“It will be obvious that many Lib Dem voters are desperately looking for a home, they no longer have a home to go in as the party’s moved away from them,” she said in her acceptance speech.
Bennett said hoped her party would "be attractive to many Labour voters and some non-voters who are totally fed up with the whole political system too."
The Australian-born former journalist stood for parliament in the London seat of Holborn and St Pancras in 2010 and the London Assembly in 2012.
On her campaign website she writes: "We cannot leave it to the Labour Party to be the sole dissenting voice to the Coalition government – it is too weak a voice and too tainted by its record in government."
Runner-up Peter Cranie, who she triumphed over in the final round of a contest fought under the STV system of proportional representation, immediately tweeted: "Thanks to everyone who supported my campaign. Count went to 2nd & 3rd prefs with @natalieben elected as leader. More later."
The party will announce the result of a vote for a new deputy leader later after delays to the vote counting forced a postponement.
Green Party equality rules mean of the two posts, a man and a woman must be elected.
Bennett will head straight into the party's autumn conference, taking place in Bristol from Friday, where she will deliver the keynote speech.