A new NHS app for contact tracing in a bid to slow the coronavirus spread must be open to proper scrutiny over its use of data, MPs have said.

Health Secretary Matt Hancock said the app will alert other users if they have been in significant contact with someone recently who now has Covid-19 symptoms.

He said developers of the app, which is currently being tested, were working with the world’s leading tech companies and experts in clinical safety and digital ethics “so that we can get this right”.

Making the announcement at the daily Downing Street press conference, he said: “If you become unwell with the symptoms of coronavirus you can securely tell this new NHS app and the app will then send an alert anonymously to other app users that you’ve been in significant contact with over the past few days.”

This should mean people can act even before they have symptoms.

Mr Hancock said in a commitment to transparency, the source code will be published, and he sought to reassure people that data will not be held any longer than is necessary.

He said: “All data will be handled according to the highest ethical and security standards and would only be used for NHS care and research and we won’t hold it any longer than it’s needed.”

While the use of technology in the coronavirus fight was welcomed by shadow health secretary Jonathan Ashworth and acting Liberal Democrat leader Sir Ed Davey, both said the use of such an app must be open to proper scrutiny.

Mr Ashworth said it is “vital to have the proper safeguards and transparency when it comes to capturing or mapping people’s data.”

Sir Ed called for “transparency”, and said it bolsters the case for an emergency recall of Parliament.

He said: “Any proposal on the use of mobile phone data or other technology to track people must also be scrutinised properly by MPs before a final decision is made, further strengthening our argument that Parliament should be recalled urgently.”

The Equality and Human Rights Commission (EHRC) said it would be offering advice to the NHS on ensuring the new technology protected user privacy.

Chief executive Rebecca Hilsenrath said: “The right to privacy is one of our most precious rights and it is good to hear the Health Secretary give assurances of handling this information with the highest ethical standards and for the shortest period necessary.

“We will be contacting the NHS to offer our advice and assistance in what they will need to consider.”

Professor Keith Neal, emeritus professor in the epidemiology of infectious diseases at the University of Nottingham, said the app could potentially be used as a route out of lockdown.

He cautioned that it will work better with widespread testing and large numbers of people using it.

Prof Neal said: “Even with only testing clinical cases in hospital it will still identify some of those at risk.

“With widespread testing it will work much better. The more users of the app the better. An option is having the app as an early route out of lockdown allowing app users less restrictions..”

Mr Hancock said: “The more people who get involved then the better informed our response to coronavirus will be and the better we can protect the NHS.”