Ms Cherry would like the power to vary the office to be devolved to Holyrood. She said concern over the lord advocate’s dual role “had increased in recent times because of some high profile cases”.

She cited the complaints investigation against Alex Salmond and the malicious prosecution scandal, the cost of which is to reach £60.5 million.

Ms Cherry lodged a private member’s bill at Westminster yesterday which would allow the Scottish Parliament itself to split the role of lord advocate into those functionally equivalent to an attorney general and director of public prosecutions.

She said in the Commons that the “historical anachronism” of the dual role could “give rise to a conflict of interest, or at the very least the perception of a conflict of interest”.

The SNP’s last manifesto had promised to “consult on whether the dual functions of the law officers, as head of the independent prosecution service and principal legal advisers to the Scottish government should be separated”.

Ms Cherry said: “Given that both criminal and civil justice are devolved matters, it is only right that the Scottish Parliament decide how best to reform the role of the lord advocate.”