New figures reveal that, of almost 300 formal complaints of racist behaviour against police officers in the past five-and-a-half years, nine were upheld, two of which led to misconduct procedures.
Since Police Scotland was established in April last year, one of 78 complaints of racist behaviour has been upheld, with the matter "concluded by explanation". In the same period, 47 of the complaints were not upheld, with the remainder abandoned, withdrawn or still being investigated.
Since 2009, the Police Investigations and Review Commissioner's office, where members of the public can turn if they are unhappy with the way their complaints have been dealt with, said it had received 11 requests for reviews into allegations of racial discrimination. In three of the cases it ruled the complaint "was not handled reasonably" by the police.
Police Scotland said officers received extensive training on equality and diversity issues, while the Scottish Police Federation said it had no concerns over how complaints were investigated.
However, MSPs and criminal defence lawyers said the statistics cast doubt over the credibility of the police when it came to investigating allegations of racism against its own officers.
Aamer Anwar, a prominent human rights lawyer who successfully sued Strathclyde Police in 1995 after he was the victim of a racially motivated assault by officers in Glasgow's west end four years earlier, branded the police complaints procedure in Scotland farcical, with the force "repeatedly finding themselves not guilty".
He cited the example of the Scottish Ethnic Private Hire Welfare Association, which has raised strong concerns about the treatment of its members by police, as evidence that discrimination within the force was not a thing of the past.
He said: "If it's happening to taxi drivers, it's happening across society. The police say they have this extremely robust complaints system, but it seems to be stacked in favour of the police.
"The racism figures are the tip of the iceberg but reflect a much bigger problem with an arrogant complaints system rigged in favour of officers who abuse the law."
Overall, since 2009/10, fewer than one per cent of complaints led to misconduct procedures, with the same proportion upheld but concluded by explanation. Five "resulted in advice".
Meanwhile, 186 complaints were either not upheld, led to no proceedings by the procurator-fiscal, which investigates criminal allegations against police, or were "unsubstantiated by available evidence". Of the 294, 40 were "resolved by explanation to complainer", meaning they were neither upheld nor thrown out. However, the category is "historical" and no longer in use, police said. Another 30 remain open, with one dating back to 2010/11.
Liberal Democrat MSP Tavish Scott said the fact just two complaints had led to disciplinary procedures in six years would "raise eyebrows".
He said: "People will have legitimate questions over how investigations have been conducted. Transparency and openness is required to ensure we can maintain confidence in the process and ministers and senior officers might wish to look again at how complaints are handled."
David Kennedy, conduct secretary for the Scottish Police Federation, said he was confident that all complaints were thoroughly and properly investigated by Police Scotland, and that officers were often victims of malicious allegations of racism.
A force spokesman said: "Police Scotland embed their commitments to equality and diversity across all areas of the business and this includes training to frontline officers in relation to hate crime and providing them with access to specialist resources who can provide guidance and assistance in relation to any diversity matter.
"All officers are cognisant of the expectation that they will treat all those they come in contact with in line with the Police Scotland values of integrity, fairness and respect."