Race relations specialist Gus John and his team studied the files of 13,000 cases finalised in the courts between September 2000 and August 2001.
"We can't conclude conclusively that there is or is not bias or discrimination in prosecutors' decision-making," conlcuded the report, published on Tuesday.
"The evidence in the files is not complete enough to allow us to do so, it said.
"What we have, however, are a series of patterns which I believe must cause the CPS some concern," the study said.
John reported that Afro-Caribbeans and Asians were sometimes "brought to trial on a less sound basis than white defendants," but this was mainly due to problems with the charges originally brought by the police.
"We need to look at the way we present objections to bail to see if there is any subconscious bias there”
director of public prosecutions
Afro-Caribbean defendants were also more likely than white defendants to have their cases dropped - for example, because evidence was no longer considered sufficient - while south Asian defendants were less likely than whites to have cases discontinued, he said.
Cases against black and south Asian defendants were also more likely to fail, John said.
And he said the CPS was more likely to object to bail for black defendants and more likely to give the reason that they would "obstruct justice" than for defendants from other ethnic groups.
"It is important that the CPS take steps now to attend to the possible explanations for the differentials this research has highlighted," John concluded.
He made 10 recommendations including appointing specialist prosecutors to deal with crimes involving racist and religious dimensions, improving the way decisions are recorded in case files and creating a more robust management structure.
Director of Public Prosecutions David Calvert-Smith said there were no grounds "for saying that the service is consciously biased against black and ethnic minorities."
But he added, "We need to look at the way we present objections to bail to see if there is any subconscious bias there.”