Ministers have been told by prosecutors to keep quiet about the details of the Peter Murrell scandal until sentencing, the Mail can reveal.

The Crown Office led by outgoing Lord Advocate Dorothy Bain, KC, has advised them to avoid giving the impression of political pressure.

Murrell’s conviction meant the proceedings are no longer considered ‘live’ for media reporting under the Contempt of Court Act because there was no trial, meaning jurors could not be prejudiced.

But it is understood the Crown Office believes that any public commentary on the detail of the case by political figures would be ‘sub judice’ and should be ‘avoided’.

Lord Advocate Dorothy Bain KC

Scottish Tory justice spokesman Stephen Kerr said: ‘This is another instance of the SNP hiding behind process to avoid giving the public the straight answers they deserve.

‘This affair stinks, and the public will not be fobbed off with the usual Nat deflections and evasions.’

The Crown guidance is surprising because judges are trained to decide cases only on the evidence, meaning public commentary is generally permitted to a much greater extent when no jury is involved.

Alistair Bonnington, former honorary professor of criminal law at the University of Glasgow, said: ‘The Crown Office statement is legally nonsensical.

‘The law is clear.

‘The Contempt of Court Act does not prevent comments from anyone at this stage.’

He added: ‘The notion that a professional High Court Judge can be influenced by anything appearing in the media is simply wrong.’

A Crown Office spokesman said: ‘The restrictions imposed by the Contempt of Court Act 1981 continue to apply until Peter Murrell is sentenced and therefore any public comment on the matter is to be avoided.’