Young black people are nine times more likely to be locked up in England and Wales than young white people, according to Ministry of Justice analysis.

The official exploratory study also shows that young black people are more likely to be identified with “gang concerns” and be considered a risk to others when being sentenced than any other ethnic group.

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The research was released on Friday, before next week’s expected publication of the final report of the landmark review into the treatment of black people by the criminal justice system. The report, commissioned by Downing Street and carried out by the Labour MP David Lammy, is expected to include strong recommendations for action.

The Lammy review was given a political boost by Theresa May when she pledged to fight racial injustice during a speech on the steps of No 10 after she became prime minister last year. “If you’re black, you’re treated more harshly by the criminal justice system than if you’re white,” she said.

An interim report by Lammy last November confirmed that people from black, Asian and minority ethnic backgrounds were more likely to be jailed for some crimes than those who were white. It revealed ethnic disparities at many stages of the criminal process, including arrest, charging, prosecution and imprisonment.

However, the MoJ analysis shows that the problem is more acute for young black people. While black people are four times more likely to be in prison than white people, the incarceration rate rises to nine times more likely for those under the age of 18.

About nine in every 10,000 young black people in the general population were locked up in young offender institutions, secure training centres or secure children’s homes in England and Wales in 2015-16. This compared with one in every 10,000 of those from white ethnic backgrounds, four in every 10,000 of those from mixed ethnic backgrounds, and two in every 10,000 of those from backgrounds classified as “Asian and other”.

The report also shows that while the overall numbers of young people aged 10-17 in the daily youth custody population has fallen sharply in recent years, from 7,096 in 2005-06 to 924 in June this year, the number from BAME backgrounds has fallen at a slower rate than those who are white.

The report said this meant their share of the custodial population has increased over the past decade. The latest figures show that 237 young black people were sentenced to youth custody in 2016 out of a total of 1,372 young people. The number of young white people imprisoned was 674 in the same period.

“The analysis in this report indicates that the high proportion of young black people in custody is likely to be driven by a number of factors such as arrest rates, custodial sentencing at the magistrates court, and the fact that they have spent longer in the custodial estate on average than other groups in the past five years,” it concludes.

The analysis also highlights a higher rate of gang affiliations as one possible factor influencing sentencing decisions. It finds that gang concerns featured in 34% of pre-sentence reports on young black men written by youth offending teams, compared with 21% for those from mixed backgrounds, 11% from Asian backgrounds and just 5% for those from white ethnic backgrounds.