The new NHS contact tracing app rolled out across England and Wales is facing scrutiny, after developers admitted not all test results can be linked to the application.

Thursday's launch of the NHS COVID-19 app follows months of delay and questions about its effectiveness.

And yesterday, one Twitter user pointed out a vital shortcoming of the system when they revealed they could not upload their own test result. 

In response, the app's official twitter account confirmed that it tests carried out in a Public Health England lab or NHS hospital cannot be linked with the app.

They said: "If your test took place in a Public Health England lab or NHS hospital, or as part of national surveillance testing conducted by the Office for National Statistics, test results cannot currently be linked with the app whether they're positive or negative."

Labour MP Jonathan Ashworth was quick to question the shortfall on social media. He said: "All want to see this app succeed. We’ve encouraged people to download it.

"But have they really launched an app that doesn’t actually link to tests carried out by NHS hospital labs & PHE labs instead only including tests carried out via the outsourced lighthouse lab network?"

Meanwhile, the 'Protect Scotland' contact tracing app was introduced on September 10, and so far over one million Scots have downloaded the app.

The app alerts users if they have been in close contact with another app user who tests positive for coronavirus and can help in determining contacts.

NHS Scotland says: "Using the Protect Scotland app, along with sticking to current public health measures, will help us to stay safe when we meet up, socialise, work or travel.

"As we see the rate of infection start to rise, it is important that we all download and use the Protect Scotland app to help stop the spread of coronavirus."

As of Thursday evening, the app in England and Wales had also been downloaded more than one million times by Android users, according to the Google Play Store.

However, the total figure is likely to be higher when iPhone downloads are included, but Apple does not provide similar figures for app downloads.

Health and Social Care Secretary Matt Hancock said the app’s launch came at a “tipping point in our efforts to control the spread of this virus”.

He told BBC Breakfast that the more people who download the new coronavirus app across England and Wales “the better”, adding it was good “for your community”.

“The more people who download this app, the more effective it will be,” he said.

Like in Scotland, as the software is voluntary, its success will also depend heavily on how many people choose to download and use it.

The Department of Health and Social Care (DHSC) said it is aware of the issue and “urgently working” to resolve it.