The Green Party's spring conference has got underway, with members urged to push for an electoral breakthrough in Westminster.

Although it has no MPs, the party is pointing to its representation in the UK's other elected bodies as proof that people want to "vote Green".

As grassroots members gathered in Chesterfield, they pointed to two MEPs, two London assembly members and seven MSPs as proof of their continued popularity.

"The message from voters is pretty clear; they want to - and do - vote Green," said Keith Taylor, one of the party's two principal speakers.

There are hopes that the next general election will see the party's first candidates elected to the Commons.

While the first-past-the-post electoral system makes it extremely difficult for the party to win any constituencies, there are hopes that four or five MPs could be returned at the expected May 5 election.

"The Green Party won the seat of Brighton Pavilion in the European elections, pushing Labour into third place with 27 per cent of the vote," said Taylor.

"If the people of Brighton vote the same way again, they will elect the first Green MP to parliament, and once there the Green Party will change the face of parliamentary politics for good."

Scottish Greens co-leader Robin Harper, who opened the conference on Wednesday, insisted the party was setting the agenda.

"Green politics still leads the way at every level of public policy: energy, transport, international affairs, human rights, housing," he said.

In the Scottish parliament the Greens "point out the inconsistencies between the Lib/Lab executive's road building policies and their unsuccessful attempts to reduce road traffic", he added.

"Greens are also leading the campaign for zero waste and a GM crops liability bill."