HYPERBOLE has always been a staple of election campaigns.

If one party promises voters the moon, another is sure to trump it by offering the stars. The electorate are used to seeing through such overblown claims.

But sometimes the language takes on a darker tone, and cannot be brushed aside.David Cameron's recent attacks on the SNP fall into this category.

There is nothing wrong with parties knocking lumps out each other over policy. Vigorous debate is the lifeblood of politics and in this election, with a £120bn gap between the Labour and Tory plans, and the SNP urging an end to austerity, there is no shortage of issues to thrash out.

But Cameron's insinuation that it would be beyond the pale, almost undemocratic, for the SNP to influence the next government is another matter. If that government was led by Labour with fewer MPs than the Conservatives it would lack "legitimacy", goes the cry, as panicking Tories try to frame the narrative that could give them a second election this year.

Nick Clegg was at it too yesterday, saying voters would question the "birthright" of a government in which a second-place Labour party was assisted by the SNP. Not only does this wilfully ignore history - half the 20 British governments of the 20th century were coalitions or minorities - it also ignores basic politics.

Voters elect parliaments not governments, and that means a myriad of combinations. Although they have been rare in recent decades, hung parliaments are not a perverse outcome but perfectly legitimate and to be expected.

Cameron and Clegg may only want to whip up votes, but by demonising SNP MPs as a hostile takeover force they risk whipping up anti-Scottish sentiment south of the border too. It is to her credit that Scottish Tory leader Ruth Davidson is having none of it.

What we heard this week was ugly, but bearable so long as it ends on May 8. It would be unforgivable if the same attacks continued after the election. Parties refusing to recognise results they dislike - now that would be undemocratic.