SNP 'would nullify 40-seat Tory lead' per BBC News

'Even if the Tories are the largest party, if there is an anti-Tory majority, my offer to Labour is to work together to keep the Tories out," Scotland's first minister said.

When pressed on whether that would apply even if Labour had secured "10, 20, 30, 40" fewer seats than Mr Cameron's party, she replied: "Governments in the House of Commons are about who can command a majority."If there is an anti-Tory majority, yes... we would work with Labour to stop the Tories getting into Downing Street."'

I forsee a political crisis if this happens.

Maybe a refusal by Conservative voters in London and the South East to pay for the policies of a Labour SNP government would be in order?