Jock Thomson QC, a former senior prosecutor, believes Kenny MacAskill and Lord Advocate Frank Mulholland have an "unhealthy alliance" which has contributed to the system's destruction.
Mr Thomson, now a defence advocate, made the claims in a letter to The Herald on the issue of the removal of corroboration in Scottish courts – which he claims is a "draconian step".
The Law Society of Scotland is also raising concerns over the removal of corroboration without other safeguards to prevent miscarriages of justice.
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: MacAskill and Mulholland, in the same bed. There is no separation of powers. Constitutionally, the system now is morally and mortally flawed." He claims a "furore" about a lack of convictions in rape cases led Mr MacAskill to instruct a report on the justice system by Lord Carloway, which has resulted in the plans to abolish the need for corroboration.
Mr Thomson added: "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."
The Law Society said it was "seriously concerned" about Mr MacAskill's refusal to reconsider the abolition of corroboration or instruct a further review by the Scottish Law Commission.
Bill McVicar, convener of the Society's criminal law committee, said: "Safeguards incorporated in other criminal jurisdictions where there is no requirement for corroboration, such as weighted majority verdicts and rules of admissibility of eye-witness identification evidence and the possibility of withdrawal of unreliable evidence by a judge from a jury are non-existent in Scottish criminal procedure precisely because there is currently a requirement for corroboration."
A Scottish Government spokesman said: "There is clear separation between the independent Crown Office and Procurator Fiscal Service and the Scottish Government. The consultation [on corroboration] specifically sought views on whether any additional safeguards would be required as a result of removing the corroboration rule and we will carefully consider all responses."
A Crown Office spokesman said: "The abolition of corroboration, recommended by Lord Carloway, is a matter for the Scottish Parliament, not the Law Officers."
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