Professor Neil Ferguson continued to act as a Government science adviser after being caught breaking Covid-19 social distancing rules to meet his married lover.
It was Professor Ferguson's advice that initially prompted Boris Johnson to put Britain in lockdown for the first time.
He sat on the government's SPI-M committee, a part of SAGE which provides advice to ministers on their response to the pandemic.
He also sat on the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag).
In May Number 10 said he had stepped down from both SAGE and Nervtag after it was revealed he had broken the rules.
Asked if he was still attending Nervtag, the Prime Minister's Official Spokesman said at the time: "Nervtag is part of Sage, so the answer is no, Professor Ferguson will no longer attend, participate or contribute to SAGE meetings."
But Professor Ferguson continued to attend meetings of Nervtag, and appeared on minutes of a meeting over the summer.
Today, the Prime Minister's Official Spokesman admitted Professor Ferguson had continued to attend the meetings - but provided no explanation for why the public had been misled.
The spokesman said: "He is one of the world's leading epidemiologists. Since he stood down he has not attended SAGE, but he continues to advise in his roles on SPI-M and Nervtag."
Scientific Pandemic Influenza Group on Modelling (SPI-M) is a sub-group of SAGE.
Professor Ferguson, an infectious disease epidemiologist at Imperial College London, said he believed he was immune to the virus after self isolating with symptoms in March.
In a statement at the time, he said: "I accept I made an error of judgement and took the wrong course of action. I have therefore stepped back from my involvement in SAGE [the government's Scientific Advisory Group for Emergencies].
“I acted in the belief that I was immune, having tested positive for coronavirus and completely isolated myself for almost two weeks after developing symptoms."
