Image copyright Getty Images Image caption Broadcasters have said the debates will go ahead regardless of who takes part

David Cameron has said "good progress" has been made on coming up with a format for TV election debates that he would be willing to take part in.

Broadcasters have granted Mr Cameron's request for the Green Party to feature in one of the debates alongside the Tories, Labour, the Lib Dems and UKIP.

The prime minister said he was "delighted" the BBC, ITV, Channel 4 and Sky had "gone away and thought again".

But he questioned why Northern Ireland parties had been left out.

The broadcasters have revised their original proposals and invited the SNP and Plaid Cymru, as well as the Green Party, to take part in two seven-leader debates while also proposing a head-to-head encounter between Mr Cameron and his Labour counterpart Ed Miliband.

'Missing out'

Asked whether he would "turn up" for the debates, scheduled to take place in April, Mr Cameron gave no commitment but indicated he was happy with the changes made.

"I was told it was appalling and outrageous that I had suggested that you could not have one minor party without having the other minor party," he said.

Current proposals - who has been invited to take part?

Sky/Channel 4: David Cameron (Conservatives) vs Ed Miliband (Labour)

ITV: David Cameron (Conservatives), Ed Miliband (Labour), Nick Clegg (Lib Dems), Nigel Farage (UKIP), Natalie Bennett (Green Party), Nicola Sturgeon (SNP), Leanne Wood (Plaid Cymru)

BBC: David Cameron (Conservatives), Ed Miliband (Labour), Nick Clegg (Lib Dems), Nigel Farage (UKIP), Natalie Bennett (Green Party), Nicola Sturgeon (SNP), Leanne Wood (Plaid Cymru)

The debates would take place on the 2nd, 16th and 30th April, with the order yet to be decided

"They have actually come up with rather more minor parties that I had in mind but I am sure they have thought it all through and they know what they are doing.

"Although I don't quite see why Northern Ireland seems to be missing out because as far as I am concerned that is as important part of the UK as Wales or Scotland."

He added: "I want to take part. They (the broadcasters) needed to do the minor party thing and they have certainly done that."

The Democratic Unionist Party and other parties in Northern Ireland have said they should take part in the multi-leader debates and warned of potential legal action if they are excluded.

'No excuses'

The broadcasters have said the debates will go ahead regardless of whether individual leaders turn up or not.

Lib Dem leader Nick Clegg said everyone would have to compromise a little for the debates to go ahead.

"I think, you know, you shouldn't be looking for excuses to wriggle out of them which appears to be the approach from the Conservative Party so far," he said.

"Look, as it happens, I'm not completely happy with the proposal because as a deputy prime minister and leader of a party of government I think I should be allowed to defend our record in government in all of the debates.

"But, look, everyone is going to have to compromise at some point, and I think that no one should be left with any excuses not to enter into those debates."