The England football team's doctor Rob Chakraverty has left his role at the Football Association.
Dr Chakraverty's position had come under intense scrutiny following revelations about his time as a medic at UK Athletics (UKA), when he was involved in a controversial procedure on four-time Olympic gold medallist Mo Farah.
He carried out an infusion of the legal supplement L-Carnitine on Farah before the 2014 London Marathon, but failed to record the levels.
"The time is now right to step away from this role and seek new challenges," Dr Chakraverty told BBC Sport.
Last month, a BBC Panorama programme about Farah's former coach Alberto Salazar found Dr Chakraverty had expressed reservations about possible "side effects" from the infusion, but went ahead anyway.
Football Association (FA) chairman Greg Clarke then revealed to BBC Sport that "internal conversations" were ongoing to do with Dr Chakraverty following the documentary.
- FA holds 'conversations' over ex-UK Athletics doctor Chakraverty
- Doctor says L-Carnitine injection not recorded correctly
- Concerns over medications for Mo Farah 'dated back to 2011'
Dr Chakraverty was at UKA from 2009 to 2016, finishing as chief medical officer.
He has been the lead performance doctor with the England men's football team since 2016.
When approached by the BBC, an FA spokesperson said: "The FA can confirm Dr Rob Chakraverty is to stand down from his role with the England senior men's team.
"We would like to offer our sincere thanks to Rob, not just for his part in the team's progress since 2016 but also in sharing his expertise across the wider medical department. We wish him every success for the future.
"A decision regarding his replacement will be made before the next England camp, whenever scheduled."
Dr Chakraverty said: "It has been a privilege to work as the lead doctor to the England men's senior team since joining the FA in 2016.
"The team and players have been wonderful to work with and the memories of what we achieved together at the World Cup two years ago will stay with me forever. The time is now right to step away from this role and seek new challenges, enabling my successor to establish themselves into the team before the next tournament.
"I would like to thank my colleagues and the players for their support and wish them every success in achieving their goals in the tournaments to come."
In 2017, Dr Chakraverty was criticised in a parliamentary hearing by then UKA chairman Ed Warner for "inexcusable" conduct over his failure to record the L-Carnitine injections given to Farah.
There are no suggestions of any wrongdoing during his time at the FA, but it has been complicated by allegations regarding his time at UKA.
In February, Clarke was asked by BBC Sport if Dr Chakraverty would be able to keep his role at the FA.
Clarke said: "I have only read what is in the press. The conversations are going on internally. When they come to fruition I will know more."
In response to BBC Panorama last month, Dr Chakraverty said: "The evidence I provided to the DCMS select committee inquiry in April 2017 was a detailed and honest account.
"Following appropriate discussions and checks on the L-Carnitine supplement, including around safety and the Wada (World Anti-Doping Authority) dosage rules, 2.7grams of L-Carnitine was given intravenously - administered via four injections totalling 13.5ml (1 x 4.5ml and 3 x 3ml injections).
"This volume, as planned, was well below the 50ml permitted during a six-hour period.
"I have not contravened any Wada or Ukad (UK Anti-Doping) rules and I have always acted in the best interests of those I treat. My due diligence checks were thorough - this is standard process, and was necessary as it was the first time I had been asked to administer L-Carnitine.
"I acknowledged to the inquiry that my usual standard of record-keeping slipped due to heavy work commitments and travel. I undertook a further update on good clinical record-keeping in response, in May 2018.
"The GMC (General Medical Council) reviewed this issue in 2018, and concluded that the case required no further action."