Runners and riders: Green Party leadership
The Green Party's first leader Caroline Lucas is standing down to concentrate on her duties as an MP and "give other people the opportunity to get well known".
Here are the four candidates in the running to replace her at the head of the party when members cast their ballots at the end of this month.
A former fashion designer, 59-year old Pippa Bartoletti says she is seen as the "high risk candidate".
"But in truth," she adds on her Facebook page "the higher risk is accepting more of the same. We don't just need a leader, we need an explosion!".
With a background in business, Ms Bartolotti has worked in the electronics industry and for the Welsh Assembly as a business consultant.
She has been leader of the Green Party in Wales since the beginning of the year and says she joined the party because she "fell in love" with its "uncompromising stance" and how it puts "principle before politics".
In the 2010 general election she stood locally in Newport West and got 1.1% of the vote. A year later she tried unsuccessfully to get a seat at the Welsh Assembly.
In March this year she appeared on the reality TV programme Come Dine With Me, where she treated her guests to a vegetarian feast of spicy lettuce soup and an egg rogan josh curry.
As leader, Ms Bartolotti says she will be tenacious with a "strong mind" and "energetic demeanour" and work hard to raise the party's profile locally and nationally.
She says the party need to get its messaging right and apply a "Green voice" to economic and political situations.
"Whether backpacking in India, living in Cuba, running businesses in London, litter picking in Maplas or stringing chillies in my kitchen, my life experiences have taught me one great thing: Never Give Up."
Natalie Bennett, 46, is an Australian-born journalist and current chair of the Camden Green Party, in North London.
She has worked for a number of publications and is a former editor of Guardian Weekly, which she left to focus on writing and politics.
She has unsuccessfully stood twice for Camden council seats and got 2.7% of the vote when she contested Holborn and St Pancras at the 2010 general election.
A self-declared feminist, Ms Bennett founded Green Party Women and is a trustee of the equality campaign group the Fawcett Society.
London Assembly member Jenny Jones, who stood to be London Mayor this year, and Green MEP Jean Lambert are both backing her for leader.
She says the party needs a "clear national direction" and "cannot drift to success". It should be working strategically to make sure it has new councillors, MEPs and MPs on the way across the country.
She thinks there is a real chance the party can treble its tally of MEPs from two to six in 2014 and get a Green councillor in every major town and city by the end of the decade.
The party needs to create a "committed, inspired Green voters - not just people who lend us their vote when they've despaired of all the others and want to protest," she says.
On the economy, she wants to "push back against 'market knows best' neo-liberalism and privatisation" and see a restructuring of the economy, with more food grown locally and more UK manufacturing.
Energy conservation and reducing demand are top of Ms Bennett's list when it comes to tackling climate change.
Backed by the current deputy leader Adrian Ramsay and former principal speaker Sian Berry, Peter Cranie, 40, is thought to be favourite to win the race.
The Scots-born father of two lives in Liverpool and is credited as the man behind re-establishing the party in the city, where it now has two councillors.
A former co-ordinator of the party's election campaigns, he stood to be an MEP for the North West region in 2009, narrowly missing out to the BNP's Nick Griffin - who he aims to unseat next time round.
He worked in retail banks in the 1990s, before turning to the public sector first as a social care worker and then as a further education lecturer.
A one-time Labour party member, Mr Cranie is an active trade unionist and claims a long-standing commitment to fighting racism and discrimination.
He has taken an "anti-austerity" stance, criticising the "light touch" regulation of the banking industry and the government's programme of cuts.
He wants the party to focus on social justice and equality and says he understands working people and those "people who face real hardship every day".
On his website he says: "I believe that our message as a party should be focused on those in our society and overseas who are most vulnerable, whether affected by lack of jobs, poor housing, or the ravages of climate change."
He is pledging to be a leader with passion and wants the party to feel "fire in its belly", with clear targets to get more MEPs and MPs.
He promises a more diverse membership, particularly by encouraging more ethnic minority members and doing more on gender equality.
Romayne Phoenix, 52, is a former teacher, artist and mother of three teenagers.
She was a councillor in the London borough of Lewisham from 2006 to 2010 and has worked as the party's London campaigns officer.
Ms Phoenix is chair of the Coalition of Resistance, which describes itself as "a broad movement of active resistance" to the coalition government's austerity drive.
She stood in the Labour held seat of Lewisham and West Penge in the 2010 general election, getting 2.1% of the vote.
She's got the backing of veteran campaigner Peter Tatchell and Derek Wall, a former principal speaker of the party.
As leader, she says she wants "to position the Green Party at the heart of the battle against austerity, privatisation and ecological vandalism".
She thinks the economic and environmental crises are "two sides of the same coin. Neither struggle exists independently of the other" and the party needs to "reject current economic and capitalist values".
"By becoming more effective allies in their defence of jobs and living standards we might hope to become the party that nurses, teachers and all workers identify with most," she says.
A better electoral strategy, building stronger local parties and growing the party membership are some of her key aims.
She is standing on a joint ticket with Dudley Green councillor Will Duckworth who wants to be deputy leader.