Thousands of defendants in England and Wales could lose the right to a jury trial under plans designed to save the criminal justice system from collapse.

Sir Brian Leveson, a former judge asked by the government to come up with proposals to tackle a record courts backlog, said he had been forced to make recommendations he did not “rejoice in”.

Historically, only defendants facing minor offences in a magistrates court have been denied the right to a jury trial, which has long been synonymous in England and Wales with the right to a fair trial.

But if Leveson’s recommendations are implemented the right could be removed for offences such as sexual assault, racially or religiously aggravated strangulation, harassment and child abduction.

Recommendations in the 378-page report published on Wednesday include:

• The creation of a new division of the crown court in which a judge and two magistrates hear “either way” offences – those in which the defendant can currently choose to be heard by either a magistrate or a jury in the crown court.

• Removing the rightto be tried in the crown court for offences that carry a maximum sentence of no more than two years.

• Reclassifying some either way offences so they can be tried only in a magistrates court.

• Trial by judge alone for serious and complex fraud cases.

• The right for all crown court defendants to elect to be tried by a judge alone.

The top three of those recommendations would save 9,000 sitting days in the crown courts, out of a current total of 110,000, according to the report – an estimate Leveson said was conservative.

He proposed that, to maximise the effectiveness of the proposals, sitting days would increase to 130,000 a year at an overall cost of approximately £1bn between 2025/26 and 2029/30.

Leveson said: “I don’t rejoice in these recommendations but I do believe they’re absolutely essential.

“Do I want to curtail jury trial? Would I like to? No … But I would ask that the report be judged not on what I am undoing, but on what I am trying to protect.”

He said in the report that there was “a real risk of total system collapse in the near future”, with victims and witnesses disengaging because they were waiting years for their case to be heard or forgetting details by the time a case came around.

“Little or no consequences for lawlessness could lead to a breakdown in law and order and society taking things into their own hands,” he wrote.

Leveson said the many financial hits suffered by the Ministry of Justice as an unprotected government department had “come home to roost”.

Responding to the report, lawyers said restricting jury trials was not the solution to the crown court backlog, which stands at 77,000 cases.

Barbara Mills KC, chair of the Bar Council, said: “Changing the fundamental structure of delivering criminal justice is not a principled response to a crisis which was not caused by that structure in the first place. As Sir Brian recognises, it is the failure to invest properly in the justice system over decades that has led to the crisis we see in the criminal courts today.

“Juries represent society and are a fundamental part of our system. And on a practical level, it remains unclear how the current resources in the system – magistrates, judges, court staff and courtroom capacity – will be able to meet the demands of the proposed new crown court bench division.”

Richard Atkinson, the president of the Law Society, said: “The proposed new division of the crown court on its own will not solve the crown court backlog. The government would have undermined our historic jury system for no effect.

“Only investment in the whole system has any chance of success – from when a criminal prosecution starts in the police station, and at all stages before a crown court case.”

However, the Magistrates’ Association welcomed the idea of a new crown court division, while stressing that the number of magistrates would need to rise by about a third.

Asked about fears that reducing rights to jury trials would disadvantage people of colour and other minorities, Leveson denied that it would lead to more miscarriages of justice.

He said that he was seeking to tackle the risk of disproportionate outcomes by including two magistrates sitting alongside a judge in the crown court bench division and calling for an increase in magistrates from under-represented communities. He also said that – while he was aware of alleged racial bias among judges – he had not witnessed it during his 35-year career on the bench.

Other recommendations in the report included increased use of out-of-court resolutions, greater use of rehabilitation programmes and health intervention programmes and increasing the maximum reduction for entering a guilty plea at the first opportunity from 33% to 40%.

Cutting the courts backlog is seen as vital to delivering the government’s tackling violence against women and girls and safer streets strategies.

The justice secretary, Shabana Mahmood, said she would consider the recommendations and respond before legislating in the autumn.

“Swifter justice requires bold reform, and that is what I asked Sir Brian Leveson to propose,” she said.