The British government announced on Tuesday plans to restrict the rights of some defendants to a jury trial in England and Wales, as it seeks to reduce a yearslong backlog of cases in the criminal courts.

In a statement to Parliament, David Lammy, the justice secretary, said he would create new “swift courts” for defendants facing a likely prison sentence of three years or less, where judges alone would decide on their guilt or innocence.

Mr. Lammy called the proposed changes, which have to be approved by lawmakers, “bold but necessary,” and added, “Jury trials will continue to be the cornerstone of the system for the most serious offenses.”

The proposals would not apply to crimes such as murder, rape and robbery, Mr. Lammy said, arguing that Britain’s current jury system was out of step with comparable countries and saying that the changes were necessary to deal with an “emergency” in the courts and to ensure justice for victims.

The announcement is intended to speed up resolution in criminal cases, some of which are set to go to trial in 2029 because of longstanding delays. Almost 80,000 cases are waiting to be heard in the Crown Court, where the most serious crimes are heard in England and Wales, a backlog that has more than doubled since 2019.

Last year, the Labour government asked a retired senior judge, Brian Leveson, to conduct the independent review into the crisis in criminal courts.

In the first part of his review, published in July, Mr. Leveson said that the pileup of cases was having “devastating impacts on the lives of victims and witnesses,” was leaving defendants in limbo and was undermining confidence in the justice system. He called for the government to reduce the number of jury trials by allowing some offenses to be decided by a single judge and others by panels of judges and magistrates.

Mr. Lammy’s proposed changes would apply to a larger pool of cases than Mr. Leveson had called for and give greater power to lone judges, rather than the panels of three recommended by the review.

But the plans announced on Tuesday had been watered down since an internal document was circulated among government departments last month. In that document, seen by The New York Times, Mr. Lammy proposed scrapping jury trials for crimes with an expected sentence of up to five years in prison, but that was reduced to three years on Tuesday.

To be enacted, the proposed changes must to be passed by Parliament. They have already met with strong criticism from opposition parties and resistance from the criminal justice system. The government could face particular objections in the House of Lords, which counts numerous senior lawyers and retired judges among its members.

Alex Chalk, who served as the previous Conservative government’s justice secretary until July last year, said in an interview that the plans went “too far.”

He conceded that Labour had inherited lengthy backlogs from the former Conservative government, and said that if he had remained in his role, he would have supported the removal of jury trials for some “really low-level” cases.

But he said that Mr. Lammy’s proposals had jumped “from keyhole surgery to amputation,” adding: “He’s gone from making an incremental change, which could be justified on the facts, to something which is a radical incursion into the right of trial by jury.”

The proposals, which would apply to England and Wales only, are partly inspired by the system in Canada, where jury trials are held only for criminal offenses where the sentence can be five years or more. Britain’s courts minister visited Toronto last month.

In the United States, by contrast, the Sixth Amendment to the Constitution guarantees a “right to a speedy and public trial, by an impartial jury,” which in practice means that people charged with a felony will always have a jury trial unless they waive that right. Smaller offenses in the United States, like speeding tickets, are often handled by judges or magistrates.

The principle of trial by jury in Britain dates to Magna Carta — a charter of rights drawn up in 1215 — but the law has evolved to mean that the vast majority of criminal cases are already heard at lower-tier magistrates’ courts rather than considered by juries. More than 82 percent of ongoing cases in England and Wales are being heard in magistrates’ courts.

Mr. Lammy said that government forecasts predicted that the backlog of Crown Court cases would hit 100,000 by 2028. Several factors have contributed to the court backlog, including closures during the Covid pandemic, a 2022 strike by public defense lawyers over pay and a Conservative government policy to cut costs by limiting the number of days on which courts could sit.

Kirsty Brimelow, vice chair of the Bar Council of England and Wales, an association representing senior lawyers, said she was skeptical that the government’s plan would significantly reduce the backlog.

“The delays are not caused by juries,” she said, “but by underinvestment and cuts to investment in the criminal justice system.”