Shadow health minister Justin Madders wrote to prime minister Theresa May last week to demand an investigation after Mr Hancock appeared in a newspaper supplement sponsored by Babylon, the private company behind GP at Hand.
In an article published in the Evening Standard under the headline: 'Health secretary Matt Hancock: "AI can augment the human factor" of medicine', Mr Hancock says he has 'become known for using this GP at Hand app' and is described as insisting it is a 'force for good'.
In the letter to the prime minister, Mr Madders said the admission that Mr Hancock had become known for using GP at Hand placed him 'in contravention of section 7.12 of the ministerial code'.
GP at Hand
The Labour shadow minister explains: 'This is because promoting pay-for-access health products, which Mr Hancock’s comments would appear to amount to, subverts the objective and principles of an NHS, free at the point of use and open to all regardless of means.
'Moreover, GP at Hand is an app created and provided by a private healthcare company called Babylon Health, run by Conservative Party associate Ali Parsa. I consequently believe Mr Hancock’s endorsement of the GP at Hand app is in direct breach of section 7.13 of the ministerial code, because Babylon Healthcare is in part reliant on government funding and Mr Hancock is promoting a product created by this firm.'
Mr Madders also demands an investigation to determine 'whether the Rt Hon Matt Hancock received any form of gift, hospitality or payment for being interviewed for this newspaper advertorial', adding that it is a 'well-established and recognised rule' that ministers should not accept anything that 'would, or might appear to place him or her under an obligation'.
Labour has previously condemned Mr Hancock over his support for GP at Hand, with shadow health secretary Jonathan Ashworth accusing him of acting irresponsibly by 'pushing an untested private health app'.
Mr Hancock - who has personally registered as a patient with GP at Hand - has repeatedly backed a wider rollout of the service since taking over as health and social care secretary in July.
In his first major speech in the post he praised GP at Hand and called for similar technology to be 'available to all', later calling for GP at Hand itself to be rolled out nationwide.
Speaking at an event hosted by Babylon in September, Mr Hancock said: 'It works brilliantly for so many patients and goes with the grain of how people access modern services. Where a new service challenges the system, the right response isn’t to reject the new service but to change the system.’
GPonline revealed earlier this year that the GP funding model may be overhauled to accommodate GP at Hand.
A DHSC spokesperson 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.
'We are working to create a tech ecosystem which allows all innovations to flourish in the NHS, a number of which were highlighted in the article.'