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Boris Johnson and chancellor Rishi Sunak could be forced to go into 14-day self-isolation if cabinet minister Alok Sharma tests positive for Covid-19, Downing Street has confirmed.

The three ministers held a 45-minute meeting in No.10 on Tuesday, the PM’s spokesperson revealed today.

On Wednesday, the business secretary fell visibly ill in the House of Commons.

Sharma is currently in self-isolation after displaying a high temperature while at the despatch box, but his test result has not yet been received, the spokesperson said.

Under the new NHS Test and Trace system, anyone who tests positive is asked to supply a full list of anyone who they have been in “close contact”, including those who have spent more than 15 minutes with a colleague at a distance of less than 2m.

No.10 stressed that the meeting of Johnson, Sunak and Sharma had observed usual social distancing rules but said that if the test-and-trace professionals advised them to go into a fortnight’s self-isolation they would do so.

“We would follow the advice which is being given by the medical experts,” the PM’s official spokesperson said.

“He did attend the meeting in No. 10, which took place before cabinet. That was a discussion on the economy. And in terms of who was present, it was the prime minister, the chancellor, and the business secretary.

“Should the secretary of state receive a positive test, then he will work with the test and trace service to share information about his recent interactions. They will be able to provide the necessary advice.

“Meetings which are taking place in No.10 are all properly socially distanced. It is not as simple as saying that if you have been in a room with someone and you test positive you are required to self isolate. The guidance sets out there is more to it than that.”

However the guidance does state that there would be need for a full discussion about any contacts within a “workplace”.

During the Commons debate yesterday, Sharma was seen wiping his face with a handkerchief several times and his opposite number in Labour’s shadow cabinet, Ed Miliband, passed him a glass of water at one point.

The PCS union, representing about 800 of Parliament’s clerks, security guards and kitchen staff, wrote to the the PM highlighting the case in saying the decision to end virtual voting was endangering the workers.

“We believe Parliament has opened too soon and the lives of PCS members, and those of our sister unions, are being put at risk unnecessarily,” general secretary Mark Serwotka wrote.

Northern Ireland Secretary Brandon Lewis stressed it was too early to suggest Mr Sharma has definitely contracted the virus.

“I don’t want to be premature because Alok, who I wish well and hope he recovers quickly, may well have had severe hay fever, we’re not sure yet,” he told BBC Radio 4’s Today programme.

“He has had a test, he is self-isolating as you say, to take the correct precaution.”