Research suggests pulse oximeters, which are clipped to a person's finger, can overstate the level of oxygen in the blood of people from ethnic minorities. Ministers want to know whether bias could have stopped patients receiving appropriate Covid treatment.

       Mr Javid said that any bias was "totally unacceptable".

       A study published last year indicated that black people were twice as likely as white people to catch Covid-19.

       People of Asian heritage were one and a half times more likely to be infected too, it found.

       The reasons why are not yet fully understood, although racism and social inequality have been suggested as factors, as well as occupation, housing and underlying health conditions.

       Asked on the BBC's Andrew Marr show whether he thought people had died of Covid because of pulse oximeters, Mr Javid said: "I think possibly yes, yes. I don't have the full facts."

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       He said there was racial bias in medical instruments, adding: "It's unintentional but it exists... a lot of these medical devices, even some of the drugs, some of the procedures, some of the textbooks, most of them are put together in majority white countries."