BBC Scotland has been accused of failing to be impartial due to “slavish” coverage of the SNP.

Alistair Bonnington, the broadcaster’s former in-house lawyer, accused the BBC of “reverential” treatment of Nicola Sturgeon’s party.

Bonnington complained directly to the broadcaster – which said it had rebutted all of his claims – and also lodged a grievance with Ofcom.

The lawyer, who worked for the BBC from 1992 to 2008, said he would expect the BBC to lose a court challenge on impartiality “comprehensively”.

He told the Scottish Daily Mail: “If a ‘breach of the duty of impartiality’ case were brought against the BBC in the Scottish courts tomorrow, I would expect the BBC to lose, and lose comprehensively.

“That's because BBC Scotland is so obviously partial in its political news output today [and because it is] slavishly biased in favour of the SNP who now form the devolved Holyrood government.”

Bonnington said that, while working for the BBC, it had been his role to “deal with accusations from political parties that BBC Scotland was failing in its legal duty to be impartial”.

The lawyer claimed that the broadcaster’s coverage of the incident which saw SNP Westminster leader Ian Blackford kicked out of the Commons for calling Johnson a liar had been “reverential”.

The National: SNP Westminster leader Ian Blackford speaks during Prime Minister’s Questions in the House of Commons, London

He complained that the BBC had not covered criticism of Blackford (above) in its report. The BBC said it could “see nothing” to justify Bonnington’s claims.

The lawyer further complained that a story about Scotland’s NHS being at “crisis point” had been covered on the BBC’s website but not on Reporting Scotland.

Durham University’s Professor Tim Luckhurst, a former editor of the Scotsman, told the Daily Mail that he thought the BBC was “under extreme pressure to do as the SNP wishes”.

He claimed that “many of the BBC's young journalists appear to have nationalist sympathies”, and called Bonnington “astute and brave”.

A BBC spokesperson said: “We responded comprehensively at the time to this correspondence [with Bonnington], rebutting the claims and standing by our journalism.”