The Justice Secretary has denied accusations of “two-tier sentencing” after new guidelines set out a defendant’s ethnicity should be considered when deciding whether to send them to prison.

The Sentencing Council published new principles for judges to follow when imposing community and custodial sentences, including whether to suspend jail time, on Wednesday.

The updated guidance, which comes into force from April, details that a pre-sentence report would usually be necessary before handing out punishment for someone of an ethnic, cultural or faith minority, alongside other groups such as young adults aged 18 to 25, women and pregnant women.

The independent body, sponsored by the Ministry of Justice, said a greater emphasis has now been placed on the “critical role” of pre-sentence reports, with more detail on when courts should request for the information to be compiled ahead of sentencing decisions.

This includes details about the circumstances of the crime and the offender.

Shadow justice secretary Robert Jenrick said in the Commons: “The new sentencing guidelines published alongside this statement will make a custodial sentence less likely for those ‘from an ethnic minority, cultural minority, and/or faith minority community’.

“Why is the Justice Secretary enshrining this double standard, this two-tier approach to sentencing? It is an inversion of the rule of law. Conservative members believe in equality under the law; why does she not?”

But the Lord Chancellor, Shabana Mahmood, replied: “As somebody from an ethnic minority background, I do not stand for any differential treatment before the law for anyone.

“There will never be a two-tier sentencing approach under my watch or under this Labour Government.”

The Sentencing Council also advises in a new section that effectiveness of a sentence depends on defendants’ circumstances, and that rehabilitative sentences can be more effective in reducing re-offending than a short term behind bars.

It also adds new evidence for deciding sentences, for example for a young person, stating: “The disadvantages young adult offenders face in the criminal justice system may be compounded for young adult offenders from an ethnic minority background.

“For some offences, there is evidence of a disparity in sentence outcomes for offenders from some ethnic minority backgrounds.”

Elsewhere, guidance that tells courts to “avoid” sending pregnant women or mothers of babies to prison unless imposing a custodial sentence was “unavoidable”, has been welcomed by campaigners.

The guidance added: “For offences that carry a mandatory minimum custodial sentence, pregnancy and the postnatal period may contribute to ‘exceptional circumstances’ that could justify not imposing the statutory minimum sentence.”

Reacting to the move, Janey Starling, co-director of feminist campaign group Level Up, said the changes are a “huge milestone” in the campaign to end imprisoning pregnant women and mothers, while lawyer Liz Forrester, from group No Births Behind Bars, said it finally recognises the “deadly impact” of prison on babies and pregnant women.

Publishing the new guidance, chairman of the Sentencing Council Lord Justice William Davis said a sentence properly tailored to individual circumstances of the offender had the “greatest likelihood” of being effective.

He said of the updated guidelines: “It will ensure that the principles for imposing community and custodial sentences continue to be consistently and transparently applied by the courts and that such sentences are the most suitable and appropriate for the offender and offence before them.”