THE SNP have criticised proposals by broadcasters to include Ukip's Nigel Farage in pre-election TV debates while excluding the Nationalists as "utterly unacceptable".

Prior to the 2010 General Election, the leaders of the three main UK parties took part in TV head-to-heads which dominated the final three weeks of campaigning and were dubbed the 3-3-3 debates.

Yesterday - with Ukip causing jitters among the Conservative, Labour and the Liberal Democrat parties after last week's by-elections - the broadcasters announced their proposals for the 2015 debates. A statement was issued jointly by the BBC, ITV, Sky News and Channel Four.

The proposals are: one debate, as happened last time, involving the leaders of the three main UK parties with David Dimbleby in the chair; one with just David Cameron and Ed Miliband, chaired by Jeremy Paxman for Sky News and Channel Four; and a third with the three party leaders plus Nigel Farage, with Julie Etchingham in the chair for ITV.

The announcement - which follows months of detailed negotiations over the format for debates next year - is said to reflect "changes in the political landscape". Ukip came top in the European elections in May and secured their first elected Commons seat last week, while the Liberal Democrats have been languishing in the polls.

It is proposed the debates would take place on April 2, 16 and 30 at locations around the UK.

In addition, the directors of BBC Scotland, Wales and Northern Ireland are writing to the leaders of the main political parties in each nation, inviting them to discuss setting up debates, to be screened in each nation be and available across the UK too.

But Angus Robertson, the SNP leader at Westminster, branded the broadcasters' proposal as "utterly unacceptable" and said the BBC and others had failed in their duty to viewers in Scotland.

"The broadcasters have the cheek to say that their proposed format factors in 'changes in the political landscape' to justify including Ukip, entirely ignoring the fact that the SNP are now by far the third largest political party in the UK."

The Prime Minister said on television he would like the debates to happen. "I'm sure we will end up with something. They happened last time and I think they were good."

But he warned it would "take the life" out of the rest of the campaign if debates only took place on television.