The Green Party is attempting to ditch its "beards and sandals" image ahead of this year's local and European elections.
The party is trumpeting its success on GM foods
The party is unveiling a new logo and a sharper, more modern look at its spring conference in Hove.
It wants 20% more Green councillors and aims to increase its number of MEPs from two to six.
Principal speaker Caroline Lucas said the Greens were targeting disaffected Labour voters.
She said she wanted to turn the party into a "credible force". which mainstream voters would take seriously at the ballot box.
"What we are trying to do is tackle myths about the Green Party.
"When we are opposed to GM foods, for example, when we are critical of nuclear power, people often say that just means you are anti- progress.
"What we are saying is that we are not against progress, but what we are in favour of is better alternatives, whether that is renewable energies or sound environmental agriculture."
Taking the leap
The party has a new logo and a new slogan, "Real Progress".
"We are looking for a house style that is more sharp and focused," Miss Lucas told BBC Radio 4's Today programme.
Despite gaining representatives in the Greater London Assembly and Scottish Parliament, the party polled less than 3% at the last general election.
"People agree with many of our policies, but they don't necessarily take the leap to vote for us, because they don't necessarily believe it will change things.
"What we have got to do is show those areas where we have really made a difference," Miss Lucas.
She said the Greens wanted to highlight the success it has had in the European campaign to tightly regulate GM foods and promote renewable energy.
Keynote speakers at the four day conference will include RMT general secretary Bob Crow, drugs campaigner Howard Marks and gay rights activist Peter Tatchell.
Other groups to be represented at Hove Town Hall will include CND, Corporate Watch, Fair Trials Abroad, Friends of the Earth, HACAN Clear Skies, Islamic Foundation for Ecology, Our World Our Say, Palestine Solidarity, the Stephen Lawrence Campaign, Sustain and the Women's Environmental Network.