THE BBC could justify the reclassification of the Liberal Democrats as a “minor party” for May’s election, the UK’s leading polling expert has claimed.

Professor John Curtice said evidence from recent opinion polls suggested the LibDems – currently being regarded as a larger party – had similar levels of support to the Scottish Greens – which is classed by the broadcaster as a minor party.

If such a move were to go ahead, it would significantly reduce the air time allotted to the LibDems during the Holyrood campaign and weaken their chances of taking part in any leaders’ debates.

The classification of the parties has been put forward in a BBC consultation on election guidelines which in the run-up to polling day also give smaller parties less entitlement to airtime coverage than major parties.

“I think the more problematic element is the justification of the Liberal Democrats as a larger party,” Curtice, professor of politics at Strathclyde University in Glasgow, told The National.

“In Holyrood 2011, the LibDems did better than the Greens, but not that well. Whether or not the LibDems should be treated equally to the SNP, the Tories and Labour is an interesting question. You can already see how the LibDems are being treated as a fourth or fifth party in UK-wide political coverage.”

He added: “I don’t think the Greens have a stronger case to be regarded as a larger party than the Liberal Democrats, but maybe the dividing line can be drawn between those two parties and the others. I’m not saying the LibDems should be reclassified, but I think the argument can be made.”

Curtice’s comments came after the Scottish Greens hit out at the classification given to them by the BBC, claiming the broadcaster had not “caught up with” changes taking place in Scottish politics which they said had seen support for the party significantly rise.

The latest TNS opinion poll published just before Christmas showed that the Greens had more than double the support of the LibDems on the regional list ballot, with nine per cent of those polled indicating they would vote Green against four per cent for the LibDems. In the TNS poll in November, support for the Greens and the LibDems stood at five per cent on the regional vote, while the latter had four per cent in the constituency section of the ballot.

The Greens have launched a petition, which has so far gathered 4,000 signatures, asking the BBC Trust to change the status they have been accorded in the draft coverage guidelines, while party co-convener Patrick Harvie and other senior members have already met senior BBC Scotland management over the issue.

A Scottish Greens spokesman said: “The major/minor distinction has little relevance in modern Scottish politics. Viewers expect balanced and relevant coverage and that is why we have urged a review of the proposed guidance.”

The BBC Trust consultation document states: “Where the larger parties are featuring regularly, the Greens should have a minimum of one appearance a week on each appropriate programme strand.”

A Scottish Liberal Democrat spokesman said: “This is a matter for the BBC to determine, not political parties. The BBC needs to take into account the democratic requirement for an open discussion of the policies and priorities of each of the main parties so that voters can make an informed choice as to who their representatives should be.”

A spokeswoman for the BBC Trust said: “The Trust is holding a public consultation on election guidelines prepared by the BBC, and anyone is welcome to make submissions. The Trust will make a final decision in February.”