THE SNP has demanded an independent regulatory probe into allegations of bias on the BBC's flagship political discussion programme Question Time.

The publicly funded broadcaster has already defended its vetting process for the show after a former Conservative MSP and a number of councillors appeared as part of the show's audience in Elgin.

Now the SNP has called on the BBC to refer itself to the independent regulator Ofcom over concerns about audience vetting.

It comes following a series of allegations of bias concerning the show in recent months.

Concerns have now been raised by SNP deputy leader Keith Brown about the political balance of the audience on Thursday’s edition of Question Time, which was recorded in Elgin.

Mary Scanlon, who served as a Conservative MSP for over a decade, appeared on the show, as a member of the audience.

Viewers took to social media after spotting Scanlon alongside a number of Conservative councillors.

Now Mr Brown has accused the programme of having a “credibility problem” and said the audience went completely against the ethos “that politicians answer questions posed by members of the public”.

He said: “The BBC has a duty not mislead its audience. The fact is the BBC’s flagship debate programme, week after week, has elected politicians and political activists masquerading as ordinary members of the public. It seriously undermines the whole ethos of the programme.

“At any time there would be serious questions to answer about credibility, but just days away from the European elections these matters strike at the very heart of the BBC’s ability to fulfil its statutory and elections obligations.

“The ethos of of Question Time is that politicians answer questions posed by members of the public.

“Enough is enough. The BBC should refer itself to Ofcom and allow them to hold an independent investigation. That’s the only way we’ll get to the heart of whether the individuals identified in the Elgin audience lied on their application forms or whether the BBC knowingly allowed these individuals to masquerade as members of the public.”

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The BBC had come under fire before the show, with accusations of a pro-Unionist panel – which featured Deputy First Minister John Swinney of the SNP, Scottish Labour leader Richard Leonard, Edinburgh West MP Christine Jardine of the LibDems, Tory MP Bim Afolami Scottish and Scottish lawyer Eilidh Douglas, a Tory Brexiteer and Amnesty International UK vice-chair.

It's not the first time there has been controversy over the way the show has been handled since Fiona Bruce took the helm in January.

In February, the director of BBC Scotland spoken out following claims of bias after the airing of its Motherwell edition of Question Time.

The show was criticised after a former UKIP candidate claimed he was invited onto the show in Motherwell to provide "more balance" to make up a shortage of conservative speakers.

It was former Coatbridge and Chryston UKIP candidate Billy Mitchell's fourth appearance on the show in Scotland.

Mr Mitchell says he was invited by the BBC to fill the audience with more right-wing voices.

Labour lodged a formal complaint about the flagship show's "unacceptable" treatment of Shadow Home Secretary Diane Abbott at the end of last month which she described as a "horrible experience"

She said she was interrupted twice as many times as justice minister Rory Stewart, the only Conservative MP on the panel, and the audience was “whipped up against her”.

Labour also objected to a clash over polling during the programme, when Ms Bruce interrupted the shadow cabinet member when she correctly claimed that recent opinion polls suggested Labour was on a level pegging with the Tories.

Ms Bruce insisted the party was “definitely” behind but later issued an on-air clarification over her comments.

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She told viewers: “I just want to pick up on something from last week’s programme. There was some discussion about opinion polls, you may aware of this.

“I was talking about a poll that came out the day of the programme that suggested the Conservatives were ahead.

“The shadow home secretary mentioned some other earlier polls which showed Labour in the lead, and we should have made that context clear, and I’m really happy to do that now.”

Responding to the criticism over the latest audience selection row, a spokesperson for the BBC said: “Question Time does not bar people from its audience because they have held elected office or are political activists.

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“There is a selection process to ensure a range of views are heard and last night’s QT audience included supporters of different political parties, including the SNP.”

The application form for the programme requires prospective guests to say whether they have previously been on the show, and when.

Guests must also reveal who they would be most likely to vote for in a General Election, how they voted in the EU referendum, and whether they are a member of a political party.