The US Justice Department is investigating allegations of state-sponsored doping by "dozens" of top athletes in Russia, according to the New York Times.
Russia's Athletics Federation is currently suspended from all competitions - including the Olympic Games in Brazil, following a vote by the IAAF in November.
It led to the acting head of Russian Athletic Federation, Vadim Zelichenok, threatening to resign.
Thirty-one athletes have tested positive for doping following retesting of samples from the 2008 Beijing Olympics.Read the full story ›
Hundreds of people have signed a petition calling for doping in sports to be made a criminal offence.
The petition on change.org was started by the former Tory sports minister Lord Moynihan.
A competitor who deliberately cheats "shreds the dreams of clean athletes with every needle they inject", it says.
So far more than 300 people have signed the appeal, which will be delivered to the Prime Minister David Cameron and John Whittingdale, secretary of state for culture, media and sport.
Mark Bonar, the doctor at the centre of the Sunday Times doping allegations scandal, had his professional services dispensed with on Friday.
The Omniya Clinic said it had terminated its working relationship with Dr Bonar after it was revealed he does not have a licence to practise medicine in the UK.
Leicester, Arsenal and Chelsea have expressed their disappointment at the doping allegations they claim are "without foundation".Read the full story ›
The chief executive of the General Medical Council has welcomed a newspaper investigation into doping claims involving a British doctor.
"I would like to thank the Sunday Times for bringing these issues to our attention", Niall Dickson said.
These are serious allegations and we will follow them up as a matter of urgency. We expect all doctors to follow our guidance - if they fail to do so they are putting their right to practise in jeopardy.
Dr Bonar does not currently hold a licence and is therefore unable to practise medicine in the UK.
Any doctor without a licence who continues to carry out the privileged duties of a doctor is committing a serious breach of our guidance, and potentially a criminal offence.
The UK Anti-Doping watchdog (Ukad) has said it is "deeply concerned and shocked" by the claims a British doctor has doped sports stars.
The Sunday Times reported that Dr Mark Bonar had been secretly filmed discussing prescribing banned performance-enhancing drugs to the "elite" sports professionals.
Ukad chief executive, Nicole Sapstead, confirmed the publicly-funded body had received allegations involving Dr Bonar in April and May 2014 during interviews with an unnamed sportsman.
Following those interviews and an investigation, UKAD found that there was nothing to indicate that Dr Bonar was governed by a sport and UKAD had no other intelligence to corroborate the sportsman's allegations.
Chairman David Kenworthy said an independent review of the allegations against it would be conducted "as soon as possible", to examine the information passed to them in 2014 and to discern if the proper procedures were followed.
"Ukad is a publicly funded body and it is correct that it be held to account for any actions it takes. That accountability rests with the independent board," he added.
An inquiry has been ordered into the anti-doping watchdog over its handling of doping allegations involving a British doctor.Read the full story ›
The chairman of UK Athletics has said that the fight against doping is “under resourced” and suggested that more sponsorship cash should be used to ensure better tests and transparency.
Ed Warner implied that sponsors could be doing more to help by staying rather than pulling out - and also suggested that football TV sponsorship money should be siphoned off for the fight against cheats.
“One of the things that sport has to do across all sport is find a way to secure more of its revenues for the fight against doping,” he told MPs on the Culture, Media and Sport committee.
Mr Warner said the International Association of Athletics Federations (IAAF) should set aside “a fixed percentage” of all its sponsorship income to spend on anti-doping measures – and also suggested football TV revenues could contribute.
He said it would “make a lot of sense” if football also handed over a “very small proportion” of its global television income to the World Anti-Doping Agency (WADA).
“Football probably wouldn’t notice the difference but WADA certainly would,” he said.