Sir Keir Starmer announced on Wednesday that he is able to leave his self-isolation after one of his children tested negative for COVID-19.
"I'm very pleased and relieved that the test result for one of my children came back negative this morning", he said on Twitter.
He also thanked the National Health Service (NHS) staff for his quick access to the test.
Mr Starmer's child was able to get an immediate test due to his wife working in an NHS hospital, where the staff and their families are entitled to Covid-19 examinations.
Due to his isolation, the Labour leader missed the Internal Market Bill debate, and Business Secretay Ed Miliband stood in for him.
Mr Starmer was also absent from Wednesday's Prime Minister's Questions, where deputy leader Angela Rayner stepped in to face off against Prime Minister Boris Johnson.
The Labour leader was told to stay at home as he awaited the results of a test for a member of his family for coronavirus, shortly after a radio phone-in on Monday.
Last Wednesday, Sir Keir accused the government of bungling the NHS's track and trace system, saying that the lack of tests is a laboratory processing problem. He then asked Prime Minister Johnson if there was a capacity issue, leading to the widespread unavailability of testing.
This follows Health Secretary Matt Hancock urging only those with symptoms or who really need it to seek coronavirus tests, despite saying in June that the public had a "duty" to get tested.
Matt Hancock is among leading politicians who had contracted the virus themselves, including the Prime Minister, who was put in intensive care.