An "unhealthy alliance" of law makers and senior figures at the Crown Office has resulted in a "morally and mortally flawed" legal system, according to a leading QC.
Jock Thomson QC, a former prosecutor, said the "destruction" of Scotland's criminal justice system has its roots in the appointment of "career prosecutors" as law officers.
Now a defence advocate, he also voiced concerns about proposals to remove the centuries-old requirement for corroboration in criminal cases.
The rule, unique to Scotland, ensures that all key evidence presented in a criminal prosecution is backed by two sources and is regarded by many as an important safeguard against miscarriages of justice. Removing the rule was among the recommendations put forward by Lord Carloway in a package of measures intended to reform Scots law.
Writing in The Herald, Mr Thomson said: "History will show that the genesis of the destruction of our criminal justice system was the appointment of career prosecutors as law officers.
"This has led to the unholy, unhealthy alliance of law officers and law makers: (Justice Secretary) Kenny MacAskill and (Lord Advocate) Frank Mulholland, in the same bed. There is no separation of powers. Constitutionally the system now is morally and mortally flawed."
Mr Thomson argued a "furore" about the lack of convictions in rape cases led the Justice Secretary to appoint Lord Carloway to look at the corroboration issue.
The QC also raised fears about any moves to scrap an accused's right to silence, saying: "Will the next inexorable draconian step be the replacement of the presumption of innocence with that of a presumption of guilt? It's beginning to look that way. And by that time there may be little or no Criminal Legal Aid."
Ministers insisted there are distinct dividing lines between themselves and prosecutors.
A Scottish Government spokesman said: "There is clear separation between the independent Crown Office and Procurator Fiscal Service and the Scottish Government."