Ukip's triumph in the European elections became a "self-fulfilling story" because the media's blanket coverage of Nigel Farage "squeezed out" other parties, Caroline Lucas has claimed.
The Green MP told Politics.co.uk part of the reason her party had been unable to match Ukip's performance was because journalists had failed to present disgruntled voters with a "more positive option" than Ukip.
She cited a Sky News graph of parties with MEPs which omitted the Green party and the failure of newspapers to omit the words 'to the Greens' after reporting that the Lib Dems had been pushed into fifth place as examples.
— Caroline Lucas (@CarolineLucas) May 26, 2014
A petition hosted by the website 38 Degrees, which has received over 35,000 signatures, points out the BBC's election programme did not feature a Green spokesperson until 02:30 in the morning.
"This stuff matters because we can see what's happened with Ukip - people have talked about them the whole time," Lucas said.
"We know that when the media jump on something it becomes self-perpetuating - the media can't innocently say 'we're repeating what people say'.
"It became a self-fulfilling story in terms of the coverage. It feels like the media were being pretty irresponsible in some cases and docile in terms of the way in which they covered Ukip."
The Greens won over 1.2 million votes, but saw their overall vote share slip in seven of Britain's 11 regions. Their national vote share was 7.9%, down 0.75% from 2009.
Lucas said Farage was a "very effective communicator" but denied the Green party had failed by comparison because the Greens lacked the financial backing by wealthy donors enjoyed by Ukip.
"I think it's true Ukip demonstrates the days of two- or even three-party politics are over," she added.
"I suppose I hesitate to welcome the phenomenon of the growth of Ukip because some of the policies are deeply unhelpful, regressive and damaging.
"It does demonstrate people are fed up with politics as usual. Our job is to try to get a fraction of the media coverage Ukip got, to say there is a more positive option here."
The e-petition complained that the Greens' gains of 178 councillors had gone largely unreported - as had the fact it is now the official opposition in Liverpool, Solihull, Islington, Lewisham and Norwich.
The petition stated: "The BBC prides itself on painting a fair and unbiased picture of events, however in this case we feel they have not done so.
"All parties should receive fair and balanced coverage, whether they be Left, Right, or Centre. This apparent news blackout of the Green Party by a much respected taxpayer funded corporation is incredibly disturbing."
The BBC denied its coverage was biased against the Green party. A spokesperson said: "Our coverage of all parties in the local and European elections has been proportionate and consistent with our guidelines on fairness and impartiality."