Matt Hancock has been accused of breaking the ministerial code after appearing to endorse a smartphone app.
Labour MP Justin Madders is demanding an investigation after the health secretary backed the use of “GP at Hand” in an Evening Standard interview.
Mr Hancock – who has his own smartphone app – has spoken positively about the “GP at Hand” app in the past.
But he was not aware his most recent comments would appear in a supplement sponsored by the app’s owner.
An Evening Standard spokesman said: “It is not normal practice for us to discuss branding or presentation of articles with interviewees so Mr Hancock would not have been made aware of these.”
The article, the spokesman added, was not an an advertorial, meaning the newspaper had full editorial control.
A Department of Health spokesman also defended the interview.
Mr Hancock’s praise for the app, which is made by private healthcare company Babylon, was simply him championing the “benefits of a range of technologies which can improve patient outcomes, free up clinicians’ time and make every pound go further”, a spokesman said.
But Mr Madders has argued the interview breaches rules on ministers becoming “associated with non-public organisations whose objectives may in any degree conflict with government policy”.
In a letter to Prime Minister Theresa May, Mr Madders says the app, which can cost £9.99 a month to use, “subverts the objective and principles” of the NHS being free at the point of service – a government policy.
He also says any endorsement of the product appears to breach rules preventing ministers “offering support” to companies which are in any way reliant on government funding.
And he asks for an investigation into whether Mr Hancock received “any form of gift, hospitality or payment for being interviewed”.
This is not the first time Mr Hancock has spoken about the app, as he acknowledged in the article.
“I’ve become known for using this GP at Hand app,” he told the Standard, going on to defend his support for the app and others like it.
“Serving some people more efficiently allows more resources for the people who don’t want to use the technology,” he said. “We should embrace technology that helps patient outcomes.”
He also listed the Babylon app, which includes GP at Hand, as among his favourite in a different part of the article.
In February, Mr Hancock, the former digital minister, became the first MP to launch his own smartphone app, when he was serving as culture secretary.
The “Matt Hancock” app is aimed at keeping his West Suffolk constituents updated on his activities through videos and picture galleries.
First-time users are greeted with a cheery video of Mr Hancock saying: “Hi I’m Matt Hancock and welcome to my app.”