One of US President Donald Trump's favoured coronavirus advisers who sparked controversy over his comments against mask-wearing and other issues has resigned.

Fox News obtained the resignation letter for Scott Atlas, who lacked relevant experience or qualifications in public health or infectious disease.

The media outlet also reported that Dr Atlas's contract was already set to expire later this week.

"I am writing to resign from my position as special adviser to the president of the United States," Dr Atlas said in his resignation letter.

He thanked Mr Trump for the honour and wished "all the best" to President-elect Joe Biden's incoming administration.

"I worked hard with a singular focus - to save lives and help Americans through this pandemic", Dr Atlas said, adding that he "always relied on the latest science and evidence, without any political consideration or influence".

Dr Atlas attracted controversy during much of his time working for the outgoing president, and his resignation comes with Covid-19 cases surging nationwide.

Both the scientific and public health community heavily disputed his expertise and qualifications for his role.

In October, he tweeted: "Masks work? NO," despite overwhelming scientific evidence proving the benefit of wearing masks.

Twitter concealed the message as misinformation.

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He also gave an interview to Russian state-controlled TV channel RT, during which he downplayed the severity of the US coronavirus spread.

In November, he urged people in Michigan to "rise up" against Covid-19 measures, such as lockdowns to slow the spread of the virus, rather than engage in an all-hands-on-deck effort to defeat the pandemic.

As of last night, the US had recorded 13,522,247 coronavirus cases and 267,844 deaths, both by far the worst tolls in the world.