Strathclyde Police, which is now part of Police Scotland, should not have commissioned its own inspector to investigate a complaint against the force, the Court of Session ruled this week following nine years of legal deliberation.
Calum Steele, general secretary of rank-and-file body the Scottish Police Federation, told Holyrood's justice sub-committee on policing that the ruling raised questions over how Scotland's new single police force would handle complaints.
English forces should not investigate complaints because of "the difference in legal system and procedures" in Scotland, Police Scotland deputy chief constable Neil Richardson told the committee.
Local councillors should not be allowed to scrutinise complaints because a councillor who is accused of a crime could end up assessing their own investigating officer, Mr Steele said.
But he also questioned "how much credence will be given to a police officer or a police force investigating its own, even under the supervision of an independent body".
Police Scotland complaints will be supervised by the new Police Investigations & Review Commissioner (PIRC), which aims to undertake independent investigations into the most serious incidents involving police.
A complaint about "overbearing or overzealous" handling of a situation would be "relatively minor", while an officer accepting a bribe or even "a free bag of chips" while in uniform would be "serious", Mr Richardson said.
According to committee member Margaret Mitchell Conservative MSP, the Scottish Police Authority has reportedly instructed local commanders "not to provide information about local police complaints to a local authority police committee".