The SNP have demanded a place in next year's General Election leaders' debates alongside David Cameron and Ed Miliband.

The nationalists said that the surge in membership in recent days meant it was now the third largest party in the UK, ahead of the Liberal Democrats.

It now has 62,000 members, a doubling of the party's numbers since the No vote in the Scottish independence ­referendum a week ago.

In 2010 three parties - Labour, the Tories and LibDems - took part in the televised debates, watched by millions of viewers. Since then both Labour and the LibDems have said that they remain committed to the same structure.

But Mr Cameron has suggested the format and timing should be changed, claiming the debates overshadowed the election.

Opponents have accused the Tory leader of running scared of the contests - and of giving extra publicity to Ukip leader Nigel Farage either by including or excluding him.

The SNP's Stewart Maxwell said his party deserved to take part in the televised debates.

"With membership of the SNP surging to over 62,000 to make the SNP the third largest party in the UK by some considerable distance, there can be no justification for the Westminster parties attempting to exclude an SNP voice from TV debates ahead of the Westminster election," he added.

His call follows similar claims from the Greens that they should take part.

Mr Clegg was judged the star of the 2010 showdowns, as "Cleggmania" swept the nation and briefly saw his party achieve more than 30% of the vote in opinion polls.

But he is also thought to have lost to the eurosceptic Mr Farage in a series of debates before the European elections earlier this year.

The independence campaign added another dimension to the history of televised leaders' debates.

Alistair Darling was widely judged to have won the first of the encounters, but Alex Salmond staged a remarkable comeback to be declared the victor of the second.

Their overall effect was widely seen as giving a boost of momentum to the Yes campaign just weeks before the vote.

SNP membership stood at 64,673 at 5pm last night.

The UK-wide Liberal Democrat membership figure is 43,451.