Lib Dem leader is wrong to question the legitimacy of a government formed by the second-largest party in parliament, says Professor Vernon Bogdanor

One of the country’s leading constitutionalists has described claims by Nick Clegg that a government would lack legitimacy if formed by the party that finished second as absurd.

Professor Vernon Bogdanor, professor of government at King’s College London, said there was a precedent for such a coalition between the smaller parties and whichever won the second largest number of seats. He added that the Liberal Democrat leader should instead be honest about whether he would politically prefer another alliance with the Conservatives.

Bogdanor, whose former students include David Cameron, whom he has described as “one of the ablest” he taught, said: “The Liberals supported the second largest party – Labour – in 1924. The implication of Clegg’s remark is that his talks with Labour after the 2010 election were mere shadow boxing. But, presumably, if he had failed to reach an agreement with the Conservatives, might the Lib Dems not have supported Labour?”

Bogdanor added of Clegg’s claims: “It is a comment about the perception of the British public. It is difficult to know how the British public would perceive [a government formed by the second-largest party]. In parliamentary terms the question is who can command support of parliament?

“[Clegg’s claim on legitimacy] is absurd. But in 1924 it was clear who would support Labour because the election was fought on the issue of free trade and there were two free trade parties. It isn’t clear now.

“Last time it seemed that the Liberal Democrats were closer to Labour on its policy on austerity and cuts. What are their views now? Which party are they closer to? They are deliberately not saying because they want to maximise their leverage. But is that fair to the voter?”

Clegg dealt a blow to the chances of a Labour-Liberal Democrat coalition in a hung parliament as he ruled out any deal that relied on “life support” from the Scottish National Party. The Lib Dem leader also argued that any coalition with the party that finished second in the election would lack legitimacy with voters, who would question the government’s “birthright”.

Cameron, however, will take comfort from Clegg’s commitment to negotiate first with the largest party. On most projections the Conservatives are expected to win more seats than Labour, although the race is tight. According to the latest Opinium/Observer poll the Tories’ lead has dropped back to one point from last week. The Conservatives are on 34%, Labour 33%, Ukip 13%, Lib Dems 9% and the Greens 6%.

Clegg’s comments further suggest that he might wish for another general election rather than be part of a coalition with Labour if Ed Miliband’s party were to come in second. Labour has long believed that Clegg, along with David Laws and Danny Alexander, would prefer to repeat the coalition of 2010.

The Lib Dem leader has previously ruled out a deal with both the SNP and Ukip. Clegg told the Financial Times he had no “meeting point” with either party because Ukip wanted to withdraw from the European Union and the SNP wanted to “pull our country to bits”.