Labour is demanding an inquiry after Matt Hancock, the health secretary, was accused of breaking the ministerial code by endorsing a private healthcare company in a sponsored newspaper supplement.

An interview with Hancock appeared in the Evening Standard’s Future London Health supplement, which was paid for by Babylon. In the feature, Hancock praised the company’s GP at Hand app, which allows users to have video consultations with doctors via their smartphone. Hancock is an ally of George Osborne, the editor of the Evening Standard.

A section in the supplement titled “Matt’s Apps” listed the Babylon product among those on the minister’s personal phone. It featured a quote from Hancock saying: “This technology allows more resources for the people visiting GPs directly.” In the interview, he said: “I’ve become known for using this GP at Hand app.”

An online version of the article stated: “This article was published in the Evening Standard’s Future London Health supplement, which has financial support from Babylon.”

The shadow health minister Justin Madders has written to Theresa May accusing Hancock of repeatedly endorsing the products of a company that receives NHS funds for every patient it treats.

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The ministerial code states that ministers should not “normally accept invitations to act as patrons of, or otherwise offer support to, pressure groups or organisations dependent in whole or in part on government funding”.

Classed as a full NHS GP practice, GP at Hand is available to people who live and work in London. Two months ago in an interview with the Daily Telegraph, Hancock called the app “revolutionary” and said he wanted it to be available to all. In the same month he spoke at Babylon’s Chelsea offices in an event hosted by Ali Parsa, the company’s CEO.

Documents released to Health Service Journal under the Freedom of Information Act in August revealed that Parsa was among 10 tech executives who met Hancock within days of his appointment as health secretary.

A source close to Hancock said the minister had no prior knowledge that Babylon was sponsoring the article which he thought was going to be about health technology.

“Matt is on record saying he wants to help [Babylon’s] competitors … he went there to say how he wants to create a tech ecosystem that lets lots of innovative companies that can help patients grow,” the source said, pointing out that Hancock has had a long-term interest in the benefits of technology across government.

A spokesman for the Department for Health and Social Care said: “As the health secretary has made clear in the past, he holds no portfolio for any particular company or brand and regularly champions the benefits of a range of technologies which can improve patient outcomes, free up clinicians’ time and make every pound go further.”

An Evening Standard statement sent to the Huffington Post said Hancock had been approached for an interview. “The interview was published as part of the Evening Standard’s Future London project within a supplement focusing on health, which was sponsored by Babylon. The articles in the supplement were not advertorials and the Evening Standard retained full editorial control over them.”