Fairer funding for Scotland and Wales will be the key negotiating demand of nationalist parties if the general election results in a hung Parliament, they indicated today.
But the leaders of the Scottish National Party and Plaid Cymru ruled out joining any formal coalition with Labour or the Conservatives should neither gain an overall majority.
They declared that an inconclusive result would be the "best possible outcome" for people in their nations as they agreed a list of four priorities to push for in talks.
Recent opinion polls have all suggested the election, expected on May 6, could leave no party with the absolute majority of seats required to form the next government.
That would result in urgent talks between the mainstream and smaller parties, aided by civil servants, in a bid to find agreements to underpin a new administration.
The SNP and Plaid today signed an agreement to join forces in any talks in an effort to secure action on four priority areas in return for their support on other measures.
Fiscal autonomy for the Scottish Parliament and a more generous funding agreement for Wales top the list which also features protecting frontline services and the most vulnerable such as OAPs and military veterans, environmental measures and extra Whitehall support for business growth.
Speaking at a joint London press conference, SNP leader Alex Salmond said: "While Westminster parties regard the prospect of a hung Parliament as a difficulty, it presents a substantial opportunity for the nations of Scotland and Wales."
And Plaid leader Ieuan Wyn Jones said a strong "Celtic bloc" of MPs "will give us a once in a generation opportunity to secure the best possible deal" for the people of the two nations.
Both parties have close experience of such negotiations as the SNP, under Mr Salmond as First Minister, runs a minority administration in the Scottish Parliament while Plaid Cymru is in coalition with Labour in the Welsh Assembly - where Mr Wyn Jones is Deputy First Minister.
Ruling out joining any formal coalition with Labour or the Tories, Mr Salmond said: "We will not form a coalition with either Tweedledum or Tweedledee.
"That would be entirely wrong and hugely difficult," he said - given their commitments to make deep public spending cuts in future years.
"All our experience from working in balanced parliaments - in my case being on the receiving end of seeing how people have managed to win concessions for their particular point of view - is that you align your achievable objectives to significant votes as they transpire in the Parliament."
Specific demands could include extending plans for a high-speed rail line to Scotland and Wales.Reuse content