Sir Keir Starmer, the Labour leader, was self-isolating for a second time on Saturday night after a member of his private office staff tested positive for coronavirus.
A spokesman for Sir Keir said he had not shown any symptoms but would be working from home in line with Government regulations.
"This afternoon, Keir Starmer was advised to self-isolate after a member of his private office staff tested positive for the coronavirus," the spokesman said. "Keir is well and not showing any symptoms."
It is understood Sir Keir will stay at his north London home until December 16, two weeks after he last came into contact with the staff member concerned.
It is the second time he has been required to self-isolate. In September, the 58-year-old went into quarantine when one of his children developed possible Covid symptoms only for a test to come back negative two days later. It is thought several members of his team are also self-isolating.
This week, Sir Keir attended the House of Commons on Wednesday before visiting a gin distillery in Southsea on Thursday and a community centre in Kentish Town on Friday. It is not clear whether he will take part in Commons proceedings next week or hand over to the deputy Labour leader, Angela Rayner.
Boris Johnson was also forced to self-isolate last month after coming into contact with an MP who later tested positive for Covid-19. The Prime Minister was contacted by NHS Test and Trace on November 15 after spending around 35 minutes with Ashfield MP Lee Anderson.
He did not suffer any symptoms and said he felt "fit as a butcher's dog" but was "following the rules" by quarantining.
Mr Johnson spent three nights in intensive care in April after falling ill with the virus and later heaped praise on the healthcare workers who saved his life.