For most of the Greens' history a collective leadership governed the party but, in October 2001, the rules were changed to create a single leadership position.

Sargent emerged victorious out of that contest six years ago. This time, Gormley is the firm favourite with McKenna the rank outsider.

But the former Dublin MEP has a loyal following and is expected, some party sources forecast, to give the new environment minister a real challenge. Almost 1,000 individuals are entitled to vote in the leadership contest.

Any paid-up party member of six months' standing will receive a ballot paper this week. They must be returned by final post on Monday 16 July. The new leader of the second-largest party in the current coalition government will be announced late on Tuesday week. Political Editor Kevin Rafter has been profiling, and talking with, the two candidates for the top job in the Green Party.

Patricia McKenna Age: 50 last March, born Castleshane, Co Monaghan.

Education: Diploma in visual education, fine art and art education.

Electoral: Elected to the European Parliament for Dublin in 1994 and again in 1999 but lost her seat in 2004. Unsuccessful Dail candidate in Dublin Central in 1992 and again in 2007.

Background: Cut her teeth working for the Green Party's first TD, Roger Garland. Won a notable legal battle in 1995 when the Supreme Court supported her argument that it was unconstitutional for the government to spend public money promoting only one side of an argument in a referendum campaign.

She has been a longtime opponent of nuclear power and genetically-modified crops. In recent times she has been vocal in criticising the Bush administration's military operations in Iraq. She has been a source of controversy over her views on vaccinations for young children.

Attitude to government: McKenna was against her party's decision to enter government with Fianna Fail and the PDs. But in seeking a nomination for the party leadership, she promised, "This will not be a campaign to rehash the decision taken in the Mansion House to go into government. I now consider that this decision has been taken and that regardless of whether one supported the proposal or opposed it we have to work with the decision and ensure that our TDs get all the backing and support they need."

Being a Green: "To be green is to want a better world. And to look at how the planet is run.

It's about putting people before profit. For me the Green Party is about ideals and beliefs. People no longer deny the fact that we have a major problem [with climate change]. Energy conservation is very popular at the moment but it's also about waste and travel but also being realistic.

I have three young kids and sometimes what is said by armchair conservationists is unrealistic because you also need to look at how people live."

Platform: McKenna surprised . . . and annoyed . . .some party members by seeking a nomination. But she believes, "It is important that there is a contest to let the public know that we are a vibrant and active party." Her pitch is that with six TDs . . . three of whom have ministerial responsibilities . . . the party would benefit from being led by a non-Oireachtas member. "John has inherited a legacy of incompetence in the department of the environment and there are also huge expectations on him from within the party, so he's going to have so much on his plate to get that job done, " McKenna says. She argues that her election would help heal any lingering ill will among the party's membership over the decision to enter government.

"We can't ignore the fact that people were unhappy about going into government. My election could create unity, " she predicts.

McKenna says her priority would be to revamp the party's organisation. "Our big challenge is going to be the local elections [in 2009]. We need a very strong structure in place to help grow the party. The challenge is not to get gobbled up by Fianna Fail. We have to maintain our identity and our own policies cannot be abandoned even if they were not included in the agreed programme for government, " she says.

John Gormley Age: 48 next month, born in Dublin.

Education: University College Dublin Electoral: After two unsuccessful attempts he won a Dail seat in Dublin South East in 1997. Held his seat in 2002 and 2007.

Background: A man of firsts . . . the first Green Party member to be elected lord mayor of Dublin (in 1994/95) he was also the first member of the Oireachtas to have his own email address.

He is his party's first minister for the environment having been appointed to the position in the recently formed Fianna Fail/ Green/PD coalition.

He has held numerous party spokespersonships in the Dail and is currently chairman of the Green Party.

Attitude to government: He once described Fianna Fail as the most corrupt political party in western Europe but now sits at the cabinet table with Bertie Ahern and 11 other senior members of Fianna Fail.

He has been a strong advocate of Green Party participation in government and, after 10 years as an opposition TD, he was open to all coalition options.

However, two days before polling in last May's general election he said his position was to "get an alternative government when the votes are counted".

Being a green: "Climate change is the number one issue. A lot of Green Party members understand that but it hasn't impinged enough yet on the public consciousness.

"Cycling is my favourite mode of transport but for personal enjoyment and for fitness not just because it's a green mode of transport.

"We eat organic food and try to live a green lifestyle. We haven't got the solar panels yet [in his house] as there's a problem with the roof but we're tackling that.

"They put long-lasting bulbs in before I arrived in the Customs House but there's still a lot of [green] stuff to be done in the building."

Platform: "At this stage in our development . . .and we've just celebrated our 25th anniversary . . . it's important that the party continues its development within government, " Gormley says.

His leadership would see the party's ruling national council feeding policy ideas into Green ministers.

"We need to make everyone feel part of this project, " he says. "We are attracting about 20 new members a day at the moment. So I think we can build on that and also attract people from the other parties into the Greens. The perception was that the Green Party was eternally in opposition and couldn't get policy through.

"Now we're in government I want the party to be seen as a party that delivers on specific issues. We have said what we can and cannot do so we have been upfront with the members and the general public."

He also wants the party to focus on the local elections with a concentration of resources on key constituencies.