Jurors of all races are more lenient to ethnic minority defendants in court in an attempt to compensate for perceived bias in the criminal justice system, according to a report published today.

Black and ethnic minority jurors are significantly less likely to convict a black or Asian defendant than a white defendant in certain cases.

“Race leniency” appeared to reflect a belief among black and Asian jurors that the courts treat defendants more harshly if they are from an ethnic minority, the report said.

It said that jurors attempted to deal with the perceived bias in the criminal justice system by trying to create a “level playing field” for ethnic minority defendants.

But the report, by the Ministry of Justice, said that such bias appeared to operate only in cases where race was not a factor in the prosecution.

“White jurors showed some same-race leniency towards white defendants, but again this was present only in cases where race was not an explicit element of the case,” it said.

“Both black and Asian jurors showed leniency for the black defendant, but there was no evidence of leniency for the Asian defendant by either Asian or black jurors.”

The study of racially mixed juries was part of a survey on diversity and fairness in the jury system carried out by Cher-yl Thomas, honorary professor at University College London.

It involved 27 simulated trials where the racial make-up of the defendant, victim and jurors was varied. “Black ethnic minority jurors showed same-race leniency towards BME defendants and were significantly less likely to vote to convict a BME defendant than a white defendant,” the report said.

“Black minority ethnic and white jurors serving on racially mixed juries appear to be particularly sensitive to the position of a black person in a criminal court, as defendant or victim.”

But the report said that this tendency towards individual bias did not influence the outcome of the jury overall. “The case was tried 27 times and there were no significant differences in jury verdicts based on the race of the defendant.”

Lord Falconer of Thoroton, QC, the Secretary of State for Justice, said: “Juries and the jury system are vital to justice. This study strongly suggests that juries and the jury system are working, and working well.”

He added: “People want the justice system to provide outcomes that are fair, unbiased and balanced. There is no complacency about justice or the justice system, but this study suggests that juries and the jury system are delivering those objectives, and delivering justice.”

Trevor Phillips, the former chairman of the Commission for Racial Equality, said: “The system can have biases even though it’s populated by people of great good will. In this case, one of the biases clearly emerges because most jurors think the system is geared against black defendants.

“This is a bias we want to avoid as much as we want to avoid a bias in favour of white defendants. All biases should be ironed out.”

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