Lord McCluskey, a former judge and solicitor general for Scotland, has urged SNP MSPs to put "the proudest traditions of Scots law" ahead of party loyalty and oppose the abolition of corroboration in criminal trials.

He said many MSPs were wary of the Government plan but "bit their lips" ahead of the referendum.

Abolishing the requirement for at least two independent pieces of corroborating evidence in criminal trials was a key policy of former SNP justice secretary Kenny MacAskill. He said it would help victims of domestic abuse, sexual assault and other crimes typically committed without independent witnesses.

Writing in a new Conservative pamphlet, Justice Matters, McCluskey said: "If the impartial, carefully considered judgment of the judiciary is to be discarded by a political vote on party lines in the feverish run-up to a constitutional referendum, then the proudest traditions of Scots law are in serious peril."