Green Euro-MP Caroline Lucas rounded on "spin, deception and lies" in a keynote speech to rally colleagues at the party's spring conference.

Dr Lucas told the assembly their party was on the brink of an electoral breakthrough.

It has members on more than 20 local authorities and a group of six, its largest, on Brighton and Hove City Council.

Dr Lucas told the conference at Hove Town Hall there could be even more come the local elections in June.

The MEP for the South-East constituency, which includes Sussex, said: "We have a proven track record of delivering on our promises once we achieve elected office. We are a party people can trust.

"Increasingly, trust counts for a lot in today's political world of spin, deception and lies.

"We also have a Government that has left so many left-of-centre voters angry, disillusioned and let down. They are finding a new political home with the Greens.

"On an increasing number of issues - war, genetically-modified (GM) food, public services and globalisation - it is the Greens that have the radical voice most in tune with what the public wants."

Dr Lucas said the Government had taken Britain into an illegal and immoral war against the wishes of the public.

On GM crops and food it had lost the economic, environmental and democratic case.

Dr Lucas said the Government was not doing enough to prevent climate change, which could cause environmental disaster and cost billions of pounds.

The Green Party was sometimes accused of being against progress but she insisted this was not true.

She said: "We're saying there's a better way of doing things - renewable energies, energy conservation, organically and environmentally-sound food and agriculture.

"We have shown it is possible to be radical and effective, progressive and competent and to be a politician and be honest."

Opening the conference, Brighton and Hove Green group convenor Keith Taylor said it was fitting the gathering should be held in the city at a time when the party was becoming a significant force in politics.

The Greens doubled their number on the council last year - the only group to do so - and took 26 per cent of the vote in the Pavilion constituency.

Councillor Taylor, who is to stand for Pavilion at the next General Election, said it was a target to win. Voters were disillusioned by what he called the old, grey parties.

Coun Taylor said when Labour held its party conference in Brighton two years ago it built a two-metre high wall around the venue to keep the public out. By contrast, the Greens welcomed members of the public into many of their events and debates in Hove.

The conference, which continues until Sunday, will discuss issues ranging from animal rights to Iraq.