The UK's judicial system is creaking, with tens of thousands of criminal cases stuck in a court backlog and jails so full that prisoners are being released early to ease the strain, with instances of convicts being freed by mistake.
Critics of Lammy's plans say years of neglect and under-investment by successive governments, not jury trials, are to blame for the state of the criminal justice system, with its crumbling court buildings and too few judges and staff.
The new measures announced by Lammy, who is also deputy prime minister, would bar defendants from opting for jury trial in cases where a jail sentence was likely to be less than three years.
Trial by jury would remain for serious offences, including murder, rape, robbery and arson.
New "Swift Courts" will be created where a judge will sit alone, taking 20 per cent less time than a jury trial, Lammy said, while complex fraud and financial trials will also become judge-only.
"I'm clear that jury trials will continue to be the cornerstone of the system for the most serious offences," Lammy told parliament.
"We now face an emergency in the courts and we must act."
The plans, which have to be approved by parliament, apply only to England and Wales.
Scotland and Northern Ireland have their own separate legal arrangements.
The government says there are about 78,000 cases awaiting trial by jury in so-called Crown Courts in England and Wales, and the number is expected to reach 100,000 by 2028, meaning victims face a lengthy wait for justice.
Some trials in London are currently expected to be heard in 2029 or 2030, and there are concerns that some complainants and witnesses are abandoning their cases as a result.
The concept of a right to trial by jury in English law was established by the Magna Carta of 1215.
However, more than 90 per cent of criminal cases are already handled by Magistrates' Courts, where a single magistrate or panel of judges adjudicates.
Under the new reforms, Lammy said magistrates' powers will be extended so they can hand down sentences of up to 18 months, meaning fewer cases will need to go to the Crown Courts.
"We're all proud of our justice system rooted in the Magna Carta. But we must never forget that it implores us not to deny or delay justice," Lammy said.
The Bar Council, which represents trial lawyers, said replacing juries with a magistrate or judge sitting alone was not the answer.
"We have continuously opposed proposals to curtail jury trials because there is no evidence that their removal would reduce the backlog, nor has it been set out how an alternative system would be resourced," Bar Council chair Barbara Mills said.
"We urge the government to reconsider pursuing radical changes under the mistaken belief that radical equals effective."
