WELSH and Scottish nationalists are "looking forward" to a hung Parliament, senior party figures said today.

The Scottish National Party and Plaid Cymru would exercise influence on a "vote-by-vote’’ basis and rather than propping up a minority administration, SNP Westminster leader Angus Robertson told a press conference in London.

With the polls currently suggesting that no party will have an overall majority at Westminster come May 7, Mr Robertson said it was an opportunity for the nationalists to swing key votes.

Speaking alongside Plaid Cymru's Adam Price, he told reporters: "When looking forward to the circumstances of a hung parliament, of course both the SNP and Plaid Cymru look forward to that circumstance with relish.

"Why? Because we would hope to be able to exercise influence, and we would do that on a vote-by-vote basis.’’ And he added: "In the current Westminster system one votes for a government proposal or against a government proposal - who one ends up in the lobbies with is not the issue at hand.’’ The nationalists had called the press conference to criticise Labour, Conservatives and the Liberal Democrats for supporting an independent nuclear deterrent.

While the Liberal Democrats have opposed a like-for-like replacement to the Trident system - backed by Labour and the Tories - the party does support an alternative system.

Mr Robertson said there was "literally no difference’’ between the three parties and insisted the UK could not afford to spend £100 billion on "weapons of mass destruction’’.

SNP and Plaid Cymru unveiled a poster spoofing Labour's manifesto cover, showing a family staring at a nuclear mushroom cloud and the words "a future feared by all’’.