The First Minister has said abolishing Trident would be "fundamental" for a deal between the SNP and any Westminster party if there is a hung parliament after next year's general election.

Nicola Sturgeon was speaking after attending a meeting in London of the Joint Ministerial Committee, which brings together UK ministers and the leaders of the devolved administrations.

She also held talks at Downing Street with Prime Minister David Cameron, who promised to do ''all he can'' to give 16 and 17-year-olds the vote in the next elections to the Scottish Parliament.

Ms Sturgeon has previously said her party would ''seek to build alliances with progressive forces across these islands'' if there is a hung parliament after May's general election.

Asked today whether abolishing Trident would be a condition for any deal with a Westminster party, she said: "For me, yes, it would be fundamental. I make no bones about this, I've never made any bones about this, I am in principle opposed to nuclear weapons.

"You add into that at the moment this economic lunacy at a time when services are under pressure, you're facing the extent and scale of public sector cuts over the next few years, to be spending £100 billion on a new generation of nuclear weapons that even many military experts now say are not required.

"I think it is a big issue and I hope that Trident and the debate around replacement and I hope non-replacement of Trident feature very strongly in the election campaign."

Ms Sturgeon renewed calls for the SNP, the Greens and Plaid Cymru to be included in general election TV debates.

She said: ''Clearly in Scotland in the period since the referendum we have seen a surge in the Greens but a considerable surge in the SNP as well. The SNP is now the third biggest party by membership in the entire UK.

''It is potentially the case that we are heading for a hung parliament where our parties may have significant influence on what happens and who forms a government.

''We are articulating it as a principle that's important to our parties, and it is. But it is a democratic principle that is very important to the electorate as well.

''If I was a voting member of the public in England I would want to hear what the SNP would do in the scenario of a hung parliament.''