Hugh Henry, the Labour convener of the Public Audit Committee, yesterday accused SNP MSPs of taking instructions from ministers instead of carrying out their parliamentary duty to scrutinise the government.
He spoke out after his committee failed to agree a report into the troubled launch of Police Scotland last year, which saw a power struggle break out between the new Chief Constable, Sir Stephen House, and Vic Emery, chairman of the Scottish Police Authority oversight body.
Mr Henry, along with fellow committee members, Labour's Ken Macintosh, Conservative Mary Scanlon and Lib Dem Tavish Scott, produced a minority report which included criticism of Justice Secretary Kenny MacAskill's handling of police force mergers.
They refused to accept an amended report, voted through by the five SNP committee members, which removed criticism of the government.
The rebels yesterday used a press conference to accuse the SNP government of pursuing a "ruthless agenda to suppress dissent".
They warned that, as a result, the parliament's committee system, which is expected to test government proposals and legislation impartially and assess the effectiveness of policies, was now failing in its duty to the public. SNP MSP James Dornan, who sits on the committee, dismissed the warnings as "sheer political opportunism".
He added: "This minority report is somewhat out of date, and it seems unaware that Police Scotland and the SPA published several documents months ago, including a detailed financial strategy, so it lacks all credibility."
Mr MacAskill said the minority report provided a historical snapshot of police reform and was outdated. He added: "The operation of committees is a matter for the Scottish Parliament."