Covid Symptom Study regrets Samantha Cameron mask ad

The masks were released as a collaboration with fashion brand Cefinn

A popular coronavirus tracking app has apologised after advertising face masks to subscribers.

The Covid Symptom Study app is run by health science company Zoe and shares its data with King's College London.

An email to users promoted silk face coverings from the brand Cefinn, run by Samantha Cameron, the former prime minister's wife.

Recipients complained they had not signed up to marketing emails when agreeing to participate in the study.

Professor Tim Spector, an epidemiologist at King's College London and the principal investigator leading the research, apologised in a second email - emphasising that all proceeds from the sales would go towards coronavirus research.

"We thought selling donated masks for charity would be a good opportunity to raise money for long Covid research," he said. "However, we did not consider the implications of working with a commercial company."

He added: "We also want to reassure you that we haven't shared your personal details with any commercial companies, and we never will. This email was, as always, sent by Zoe, the healthcare company behind the app.

"I want to personally apologise for this, and assure you that all of us here at the Covid Symptom Study will learn from this experience."

Samantha Cameron modelled one of the masks

The initial email featured images of the silk face coverings, with links to the shop. It also contained an image of Samantha Cameron wearing the mask.

They are priced at £25 each and some designs have now sold out.

"We are proud to announce that we have partnered with womenswear brand Cefinn to bring you a collection of beautiful limited edition silk face coverings," the email said.

"100% of sales from the sale of Cefinn masks will go toward funding the ground-breaking research that is being conducted at King's College London to understand the long-term effects of Covid-19."

A range of designs were released

But many have said they will now delete the app and personal data.