Member of Parliament Nadine Dorries, who is also a British minister in the health department , has tested positive for coronavirus, she said in a statement on Tuesday.
"I can confirm I have tested positive for coronavirus… and have been self-isolating at home," said the Conservative MP.
Health officials are now trying to trace where she contracted the virus and who she has been in contact with, she added.
Dorries, who helped craft the legislation to fight the bug, is the first British politician to be diagnosed with COVID-19, raising immediate concern about whether she has spread the infection.
The Times reported that she had been in touch with hundreds of people, including Prime Minister Boris Johnson.
She fell unwell on Friday while signing the document that declared coronavirus a notifiable disease, meaning companies could obtain insurance cover, said the paper, adding she was now believed to be on the road to recovery.
"I would like to thank… the wonderful NHS staff who have provided me with advice and support," she said, referring to Britain's National Health Service.
The shock news is likely to increase calls to suspend parliament, despite the government's reluctance to do so in the middle of a health crisis.
Six people have died in Britain from the virus, with 373 confirmed cases
Dorries said she took "all the advised precautions" as soon as she was told of her diagnosis.
"Public Health England has started detailed contact tracing and the department and my parliamentary office are closely following their advice," she said in a statement issued through the UK's health department.
The Times reported that Dorries met hundreds of people in Parliament in the past week and attended a reception with Prime Minister Boris Johnson.
Britain's health minister, Matt Hancock, tweeted that he was "really sorry" to hear of Dorries' diagnosis. "She has done the right thing by self isolating at home," he said.