More than a quarter of law firms and legal departments say they are using generative AI (Gen AI) technology, a sharp increase in users over the past 12 months, according to a Thomson Reuters study.

The 2025 Generative AI in Professional Services Report, which is based on a survey of 1,700 professionals mainly from the US, Canada, the UK and Australia, found that 26% of firms and in-house teams are using Gen AI, up from 14% a year ago.

At the same time, the number of law firms that think Gen AI should be used for legal work also increased, rising to 59% from 51% a year ago. A third of law firm professionals say they use Gen AI tools at least once a day.

Thomson Reuters said that part of the increased usage is being driven by clients, with 59% of corporate law department respondents saying they want their law firms to use Gen AI.

Steve Assie, general manager for global large law firms at Thomson Reuters, said: “Law firm professionals and the law firms themselves are increasingly keen to make more use of Gen AI. What’s also clear is that clients of law firms are also asking them to take advantage of Gen AI. They see improved productivity that Gen AI can deliver as being in their best interest as clients.”

Assie added that 8% of clients are now requesting in their official tender documents for firms to use Gen AI.

The survey found that 77% of law firm professionals are using Gen AI for reviewing documents, with 77% of all legal professionals using it for summarising documents. Another 74% of law firm professionals said they are using Gen AI for legal research, while 59% are using it to draft briefs or memos and 58% are using it to draft contracts.

While the report highlights increased adoption of Gen AI, few firms are measuring whether they are getting value for money out of their AI use, with just 20% measuring the return on investment (ROI) of their Gen AI investments. Of the fifth of respondents who are measuring ROI, 79% are tracking cost savings, 64% employee usage, 51% employee satisfaction and 38% client satisfaction.

Meantime, 36% of respondents said the biggest risk to the legal profession from Gen AI is the unauthorised practice of law, meaning either non-lawyers or AI itself performing the work of lawyers. Only 15% of lawyers were concerned that the impact on jobs was a major risk.

Assie added: “A consensus is building, and one we firmly believe, that Gen AI is not going to replace lawyers, it is going to be used as a tool by them. A lawyer will still need to review and verify the output of any Gen AI tool which is why the use of Gen AI by untrained and unregulated members of the public to answer legal questions is seen as a risk.”

The 1,702 survey respondents were based across a selection of countries including the US (42%), Canada (15%) and the UK and Australia (both 12%) of whom 30% were from law firms and 11% were based in corporate legal departments (11%).

In a speech delivered to the LawtechUK Generative AI Event in London in February, Master of the Rolls Sir Geoffrey Vos said lawyers and judges have “no real choice” about whether they embrace AI, but there are very good reasons why they should.

Vos said part of the reason is that their clients will be using the technology, but also because one of the biggest fields of legal activity in the coming years is likely to be around AI issues.