The all-clear came hours after it was revealed that Mr Sharma had a 45-minute meeting with Boris Johnson and Rishi Sunak shortly before falling ill, raising the prospect that the prime minister and chancellor might have to self-isolate for 14 days as recent contacts of a Covid-19 carrier under the test-and-trace system.
Downing Street said that the PM would "follow the medical guidance" but made clear that he was not expecting to be treated as being at risk of infection, as the talks in No 10's cabinet room were “properly socially distanced” with the trio more than two metres apart at all times.
Mr Johnson's official spokesman stressed that the Department of Health guidelines define a contact as someone with whom a patient has had face-to-face contact with from less than a metre or been within a distance of less than two metres for more than 15 minutes, which did not apply to the PM and chancellor due to the precautions taken during the meeting.
Speaking before Mr Sharma received his negative result, the spokesman cautioned against the assumption that the PM would be regarded as a contact under the test and trace system, telling reporters: "It's not as simple as saying that if you have been in a room with someone who tests positive for coronavirus you are required to self-isolate."
The cabinet room where the meeting took place was "vigorously cleaned" on a daily basis as a matter of routine, he added.
The requirement for contacts to self-isolate for 14 days includes people, like the prime minister, who have already suffered a bout of Covid-19, as there is so far no definitive proof that having hd the infection confers immunity.
Wednesday's early-morning meeting on economic policy in No 10 was the only time Mr Johnson has met Mr Sharma face-to-face in recent days, as the business secretary took part in other discussions - including the cabinet meeting later the same day - by video conference.
Hours after speaking with the PM, Mr Sharma was seen wiping his brow with a handkerchief several times and was passed a glass of water by his opposite number, Ed Miliband, during a debate in the House of Commons.
A spokesman for the business secretary later confirmed he had undertaken a Covid-19 test and gone into self-isolation.
And on Thursday afternoon, a spokeswoman announced: “Business Secretary Alok Sharma has received a negative result after being tested for coronavirus yesterday.
“Mr Sharma would like to thank the parliamentary authorities and Speaker and also for the kind words from parliamentary colleagues and others who have expressed their well wishes over the last 24 hours.”
The incident has fuelled calls for a rethink of Jacob Rees-Mogg's decision to ditch the "virtual parliament" system introduced earlier in the pandemic and force most MPs to return to Westminster to debate and vote.
Welcoming news of the minister's test result, veteran Labour MP Barry Sheerman - who at 79 is one of the MPs allowed a proxy vote because they are regarded as particularly vulnerable due to their age - tweeted: "Very relieved that Alok Sharma has tested negative for Covid-19. Doesn’t mean that the reintroduction of physical presence voting is not stupid!"
Liberal Democrat MP Daisy Cooper said: "This should still be a wake-up call for Rees-Mogg. The government should lead by example - support people to work from home where they can (as per its own guidance), embrace digital and stop needlessly risking health of MPs and staff."
Speaker Lindsay Hoyle has granted MPs an emergency debate next Monday on the arrangements - which forced them to spend hours in a kilometre-long queue snaking around parliament.
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