Natalie Bennett will stand down as Green Party leader this summer, when her second two-year term expires in August. Bennett said she plans to stay "fully engaged" in Green Party politics and reflected that she was "proud to lead a party through a period of phenomenal expansion and increased impact".

Bennett took over as Green Party leader from Caroline Lucas, MP for Brighton Pavilion, and shot to prominence during last year's general election campaign when she went head-to-head with fellow leaders – including David Cameron and Ed Miliband – in televised debates. Despite helping to raise the party's profile and upping its numbers from 13,000 to 60,000 members, Bennett failed to win a seat in Parliament.

In this year's May elections, the Greens failed to make significant progress and lost four councillors in local elections across England. It did, however, manage to secure its best ever result in the race for City Hall, with Sian Berry securing 5.8% of the vote for London Mayor.

In a statement, Bennett said: "I have been proud to lead a party through a period of phenomenal expansion and increased impact." She added: "With the support of our passionate members and supporters we have been able to achieve much in a relatively short period.The Green Party offers a genuine alternative to the tired status quo and I am proud that Greens do politics differently.

"There's greatly increased public understanding that when you want the honest, caring, committed view – one that isn't guided by the views of the latest focus group or fear of a tabloid backlash but by fundamental principles and values - you should come to the Green Party.

Natalie Bennett
Natalie Bennett has led the Green Party since 2012 after replacing Caroline Lucas. Phil Noble/Reuters

"Looking to the future, in which I intend to remain fully engaged in Green Party politics, I'm confident the Green Party is going to become increasingly influential on the political scene.

"We're the only party with a platform that recognises the essential interrelationship between economic and environmental justice - that we must have a society in which no one fears hunger or homelessness while we collectively live within the environmental limits of our one fragile planet."

Bennett came under heavy criticism last year when she blamed "brain fade" for her failure to explain Green Party policy. She apologised to the party's members for her poor performance.

Green Party leader Natalie Bennett
Natalie Bennett contributed to raising the Green Party's profile, helping its numbers rise from 13,000 to 60,000 members. Getty

Reflecting on her time as leader, Bennett told the Guardian: "There have been times when I got things right, and times when I got things wrong, but that's because I'm not a smooth, spin-trained, lifelong politician. It's both my strength and my weakness that I answer the question."

Nominations for Bennett's successor will open on 1 June and proceedings will close on 30 June. A one-month balloting period will commence on 24 July, the result of which is due to be announced at the party's Autumn conference in September.