She told delegates: “We have enjoyed our best ever General Election results, winning more than a quarter of a million votes and increasing our vote share by an amazing 18% in those constituencies in which we stood. We can rightly be proud of these achievements.

“But we can also - rightly - be angry that those quarter of a million voters are still being denied a Green voice in Parliament - that our shameful and manifestly unjust electoral system has denied us even one single MP at Westminster.”

In a wide-ranging speech, Dr Lucas – South East England’s Green Party Euro-MP, criticised the Government on climate change, the war in Iraq, its response to the London bombs and its attempts to undermine civil liberties and human rights.

She said the Tories and Liberal democrats had failed to give effective opposition – and criticised their failure to state the link between the war in Iraq and the London bombs.

“Those of us who state that there is a link between Iraq and the suicide bombings in London are not condoning violence. We’re seeking to explain it: we owe it to the victims to try to analyse and address the root causes of terrorism to try to prevent further attacks.”