A plan to roll out virtual legal assistants powered by artificial intelligence to crown courts has prompted warnings that the technology should not be used to “replace vital funding and additional court staff”.

David Lammy, the deputy prime minister, will announce on Tuesday that AI assistants will be trialled in an effort to cut the backlog of court cases in England and Wales.

Judges are already planning to use a new AI tool to help identify trial-ready cases and group similar hearings together, the Ministry of Justice said.

But the Law Society, which represents more than 200,000 solicitors, has said that the technology should not be used to reduce staffing costs and the pilot must be “thoroughly evaluated”.

Last year, two cases were blighted by made-up case-law citations that were either definitely or suspected to have been generated by AI.

In a speech at London Tech Week, Lammy will say: “Artificial intelligence has the power to transform how we live, work and govern for the better.

“This impact for good can be seen in our justice system, with thousands of days of admin work saved for our probation staff and the advent of new tools which aim to cut court backlogs and deliver swifter justice for victims.”

There are concerns about the dangers of ramping up the use of AI. A review into the banning of Maccabi Tel Aviv football fans from attending a match against Aston Villa in November 2025 found an “AI hallucination” produced by Microsoft Copilot had helped police justify the decision. A nonexistent game between Tel Aviv and West Ham had been referenced in a report produced by police prior to the game.

Ian Jeffery, the chief executive of the Law Society of England and Wales, said: “For the use of AI in the crown court to be effective, the pilot must be thoroughly evaluated. The outcomes of these evaluations, along with the impact of AI on the justice system, should be made public.

“While new technology should enhance access to justice, it cannot replace vital funding and additional court staff. Robust safeguards are needed to protect us all and preserve the integrity of the justice system.”

Last year, in a £89m damages case against the Qatar National Bank, the claimants made 45 case law citations, 18 of which turned out to be fictitious. The claimant admitted using publicly available AI tools and his solicitor accepted he cited the sham authorities.

Separately, when Haringey Law Centre challenged the London borough of Haringey over its alleged failure to provide its client with temporary accommodation, its lawyer cited phantom case law five times. Suspicions were raised when the solicitor defending the council had to repeatedly query why they could not find any trace of the supposed authorities.

The number of cases waiting to be dealt with by crown courts in England and Wales hit a record high of more than 80,000 cases this year, more than double the pre-Covid pandemic 2019 figure of 38,108.

Figures obtained under freedom of information laws showed 2,600 crown court trials in England and Wales were not listed until at least 2028, with 29 not due to be heard until 2030.

The government has announced plans to scale back jury trials to try to overhaul the justice system and cut the backlog.