In a parliamentary answer, Narayan said the government's own, more recent assessment is that AI adoption and data investment could add £55 billion to £140 billion by 2030, with a central estimate of £120 billion, which he called "hugely uncertain." That is less than a third of the earlier number.
The answer did not withdraw the £400 billion claim or say it was wrong.
Ministers have reportedly had the lower estimate since at least November 2025, yet Skills England, the apprenticeships agency, was still publishing the old number four months later.
Former technology minister Peter Kyle also cited it.
Dame Chi Onwurah, who chairs the Commons Science, Innovation and Technology Committee, said overstating the benefits of technology risks undermining the case for change.
Lord Holmes of Richmond, who asked ministers about the figure's origins in January 2025 without getting a reply, said the government should have clarified it sooner, noting that billions of pounds depend on robust data.
Sumedha Deshmukh of the Ada Lovelace Institute said it was concerning that ministers cited research paid for by Google for so long.
PF Global's head of economics, Jonathan Dupont, attributed part of the difference to slower AI adoption than its 2023 model assumed, saying the government's numbers reflect that. He said the firm's own central estimate for what is achievable by 2030 is now much closer to the government's, with growth picking up in the years after, and that its view of AI's overall potential has not changed. The firm said its work for Google continues but that its research is independent and its judgments and assumptions are its own. The Ada Lovelace Institute urged the government to test figures before building policy on them, fund independent research and track whether promised gains materialize. The Cabinet Office and Google were approached for comment.