Greens hoping to put down roots at Westminster

The party is aiming to finally make a breakthrough at Westminster by gaining a seat in Brighton and hopes its parliamentary campaign in this region will help it win more seats on councils.

Its manifesto includes eye-catching – and expensive – policies such as scrapping prescription charges and tuition fees. But regional co-ordinator Martin Deane insisted the party's sums did add up thanks to its plans for huge tax hikes for the wealthy.

"The point the other three parties are missing out is that Britain is still an incredibly rich country," he said. "They're not looking for where that money is in the same way we are."

Although the party is fielding parliamentary candidates in 21 seats, the real target is to improve its share of the vote in council elections and pick up extra town hall seats.

The parliamentary constituencies have been chosen according to where the party – which has around 10,000 members nationally – has a base of activists.

The Greens are pushing a message of social justice, but they have seen other major parties becoming more environmentally-conscious and committed to tackling climate change.

Mr Deane insisted this did not make the party irrelevant, saying: "For our best policies we don't have much of a problem if they're going to nick them. I don't have a problem with the leading parties becoming green, but what you get is green wash."