The government is currently trialling the app on the Isle of Wight as part of attempts to track and mitigate the spread of the virus.

ProPrivacy said that the decision to opt for a centralised model of data storage, where data is stored on a central server, risk user privacy and would potentially mean fewer people download the app.

Opting for a decentralised model, whereby data is stored on the device the app is installed on, would increase its popularity, ProPrivacy said, which would mean the app had a higher chance of stopping the spread of Covid-19.

ProPrivacy has published an open letter to the health secretary, Matt Hancock, about its proposals for the app.

Tom Chivers, digital privacy advocate, ProPrivacy, said in a statement: "While the UK government may have legitimate reasons for wanting to utilise a centralised data model for the NHSX contact-tracing app, I believe it is going to have to compromise on this if it is going to bring the public on-side and get the numbers it needs for it to be effective."