The BBC had said it will not include the Green party in next year’s proposed 2015 General Election TV leader debates, rejecting demands that the party should receive the same coverage as Ukip.
The broadcaster argued that Ukip has seen a substantial increase in support unlike the Greens.
But the Green party responded by accusing the BBC of concentrating too much on its past performance.
Earlier this month, the BBC, ITV, Sky and Channel 4 announced joint plans to hold three debates in the six weeks before polling day. One would be a head-to-head between Mr Cameron and Mr Miliband. The second would involve these two leaders and Nick Clegg, while the third would also include Mr Farage.
As it emerged that the Green party faced exclusion, almost 200,000 people signed an online petition calling for the party to received equal coverage to Ukip as both have an MP.
In a letter to the Green party’s director of communications seen by the Guardian, the BBC said: “Ukip has demonstrated a substantial increase in electoral support since 2014 across a range of elections” supported by a robust trend across a range of opinion polls.
It added that opinion polls do not yet show that the Greens are currently at a level pegging with Nick Clegg’s party.
“Even if they did, we would still, of course, be taking as our starting point the result of the 2010 general election, where the Lib Dems took more than 50 seats and 23% share of the vote, demonstrating a level of electoral support overall substantially ahead of the Green party,” the letter continued.
The broadcaster added that it will “keep any new evidence of increased support for the Green party under close review” and said that if the debates are successful it would consider “offering appropriate opportunities to other political parties” in line with its obligation to be impartial.
In a response seen by the Guardian, Green party leader Natalie Bennett criticised the BBC for concentrating on its past performance rather than looking at current polling data for the Greens and the Liberal Democrats.
Bennett cites a piece by leading pollster Peter Kellner which describes how the Greens are closing in on the Liberal Democrats as painting a realistic picture of where the Greens are in the political landscape, and said the party is concerned that the BBC is basing the debates on the results of the 2010 General Election.
“This demonstrates very clearly how the BBC appears to be acting as a worrying brake on democratic change; I believe they are failing to grasp that the future of politics doesn’t look like the past,” she said.
She added that “more people are recognising every day that the business as usual approach to economics, society, environment and politics is now untenable.
“This BBC attitude is contributing dangerously to the buildup of frustration and disillusionment with politics in the UK. We have seen nearly 200,000 people sign a petition demanding that Greens be included in the leaders’ debates based on natural justice and fairness."
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