Trident will be a central issue in the General Election campaign in Scotland, Nicola Sturgeon has indicated, making clear that Labour's agreement not to renew the nuclear weapons system would be a pre-condition of any SNP deal to prop up a minority Miliband Government.

The First Minister told a briefing at Westminster: "I hope Trident and the debate around the replacement or non-replacement of Trident features very strongly in the election campaign."

While the Scottish Labour Party opposes the renewal of Trident, Jim Murphy, its new leader, is against such a policy; describing himself as a multi-lateralist.

But asked if abolishing Trident would be a condition for any post-election deal with Ed Miliband and the UK Labour Party, Ms Sturgeon replied: "For me, yes, it would be pretty fundamental. I'm in principle opposed to nuclear weapons."

She described as "economic lunacy" the intention to spend £100bn on the renewal of Trident given the scale of cuts being endured by public services and when many defence experts no longer regarded nuclear weapons as a sensible way to defend Britain .

Meantime, Ms Sturgeon together with Leanne Wood, the leader of Plaid Cymru, and Natalie Bennett, the leader of the Greens in England and Wales, joined forces to stress how they would unite "whenever possible to battle the Westminster parties' obsession with austerity".

The FM complained that there was no end in sight to the austerity programme and that the Chancellor George Osborne in his Autumn Statement set out another £15bn of cuts for Scotland.

She insisted: "It is time for a new approach to UK politics and for our parties to use their influence to bring about progressive change at Westminster."