Google has confirmed that one of its senior executives participated in the UK government’s scientific advisory group on Covid-19, raising further questions about the composition of the secretive committee.

Demis Hassabis, a co–founder of Google’s artificial intelligence division, DeepMind, attended a meeting of the scientific advisory group for emergencies (Sage) on 18 March, when the group was considering whether the UK should go into lockdown.

Google said Hassabis was invited by the chief scientific adviser, Sir Patrick Vallance, who chairs Sage, which provides top-level guidance to the Cabinet Office during emergencies.

While Hassabis is considered a world-leading AI researcher, the presence on Sage of an executive from a Silicon Valley company that has been exploring ways to profit from using big data in the health industry is likely to deepen controversy about the group.

DeepMind previously processed millions of healthcare records from an NHS hospital trust as part of a scheme to design a diagnostic app, in an arrangement subsequently found to have contravened data protection law. DeepMind’s health unit was transferred to the parent company’s health division last year.

Also last year, Google struck a deal with the US hospital chain Ascension giving it access to the health data of millions of Americans.

A spokesperson for Google’s DeepMind said: “Demis was one of several scientists asked to contribute his thoughts on the government’s response to Covid-19.”

The spokesperson said Hassabis was a full participant in the meeting and was not required to sign a non-disclosure agreement. The spokesperson said they did not know whether the request to involve Hassabis in Sage came from the prime minister’s chief adviser, Dominic Cummings, as has been reported.

The Guardian revealed last week that Cummings and Ben Warner, a Downing Street data scientist with whom Cummings worked on the Vote Leave campaign for Brexit, have been attending meetings of the group.

Warner is a former principal at Faculty, an artificial intelligence startup run by his brother Marc Warner, which is currently working on an “unprecedented” health data-mining operation that is part of the government’s response to the coronavirus outbreak.

Downing Street is not denying this is the first time No 10 political advisers have attended Sage, which is supposed to be an independent and impartial body. However, the prime minister’s spokespeople insist it is “entirely right” that the pair should attend, insisting they have largely been silent observers in meetings.

A Downing Street spokesperson said it was “factually wrong and damaging to sensible public debate” to imply Sage’s advice to the committee had been “affected by government advisers listening to discussions”.

However, several Sage attendees have told the Guardian that Cummings and Warner have been active participants in meetings. On Tuesday Bloomberg News reported that at the same 18 March meeting, Cummings pressured Sage to recommend that the UK adopt lockdown measures to halt the transmission of the virus.

Citing people familiar with the meeting, the report said the prime minister’s chief adviser “swayed the discussion toward faster action, and made clear he thought pubs and restaurants should be closed within two days”.

It is not known what if anything Cummings or Warner were advocating in Sage earlier in that month, a period when the UK government was talking about building “herd immunity” in the population and delaying physical distancing measures.

The Guardian’s publication last week of a leaked list of Sage attendees at a 23 March meeting raised questions about lack of diversity on the group. Anthony Costello, a former director at the World Health Organization and a critic of the government’s handling of Covid-19, has complained the group lacks diversity of expertise.

On Wednesday the government dispatched invitations to academics looking for additional participants in the Sage meetings, amid concerns about a lack of expertise in areas such as nursing and public health. A note from the Government Office for Science said the group was “now looking for additional expert support”.

Vallance has reversed his decision to keep secret the names of participants in meetings of Sage and its three advisory subcommittees. On Monday he said membership of the advisory groups would be published shortly, although individual members could ask to remain anonymous.