the Liberal Democrats in a new opinion poll

The Green party has taken a small lead over the Liberal Democrats in a new opinion poll, prompting demands for the broadcasters to acknowledge a “political revolution” under way in Britain and include the party in the television general election debates.

As a veteran polling analyst suggested that Laborious standing may be inflated by shy Tory voters, who are reluctant to express support for the Conservatives, an opinion poll by Lord Ashcroft placed the Greens up three points on 11%, giving the party a small lead over the Liberal Democrats, whose vote share increased by one point to 9%.

Caroline Lucas, the Green party MP for Brighton Pavilion, said that the poll findings and the doubling in the party’s membership in the past two months showed that her party should now be included in the television debates. “There really is a political revolution going on here and it just seems so perverse that the broadcasters and Of com seem to be turning their face against it,” she said.

“They seem to be the only people in the country with their fingers in the ears and their hands over their eyes and simply not hearing the fact that something big is happening in British politics.”

The Greens have stepped up their campaign to be included in the debates by releasing a poster, featuring Lucas and the Green party leader, Natalie Bennett, which says: “What are you afraid of, boys?” David Cameron has said that he will not take part in television debates unless the Greens are included. Tory sources acknowledge in private that the prime minister’s new found interest in the Greens is designed to find him a way of avoiding the debates without being seen to kill them off.

The broadcasters are proposing three debates. One would be between Cameron and Ed Millibar, one would feature the two main party leaders plus Nick Cl egg while another debate would feature the three Westminster leaders plus Nigel Far age.

The Greens have not been invited because the broadcasters anticipated the recent suggestion by Of com that Skip should count as a major party while the Greens should be a minor party. Of com makes its judgments based on the performance of parties in elections rather than in opinion polls.

The renewed row over the debates came as the veteran polling analyst Rob Hayward suggested that opinion polls may be overstating Labour’s support by as much as four percentage points.