After a decade in Parliament, a political analyst says the Green Party is sporting a 'bland' new image and its biggest achievement is that it has survived.

The party is celebrating 10 years since entering Parliament when then-leader Jeanette Fitzsimons won the Coromandel electorate. A decade later, the Greens have nine MPs in the House based on seven percent of the vote.

Dr Bryce Edwards from Otago University says the Greens have changed a lot since then, with the last campaign showing off a slick and professional new image. He says the party has changed over the years and no longer stresses radicalism, tending to take a middle of the road path with a focus on environmental issues.

Dr Edwards says out of dozens of parties which have started since the early 90s, only the Greens have lasted the distance. He says parties such as the Alliance and New Zealand First were elected to Parliament but have not managed to remain there and be successful in an electoral sense. Dr Edwards says 10 years in Parliament shows the Greens have a niche and a following that has endurance.

Present Greens co-leader Russel Norman believes his party has made Parliament and the country better places. He says it has championed the environment and worked to keep the old parties honest. Dr Norman says while making a significant contribution in terms of policy, Green MPs have also improved the culture of Parliament by making it a slightly more constructive place than it was before. He says the party's secret to success has been sticking to its values. He says the party will continue to push for sustainability, fairness, peace and democracy and in turn, grow its support base.

The Greens are celebrating the anniversary with a birthday cake.