The London 2012 Olympics were “corrupted on an unprecedented scale” by Russia’s government and sports authorities, who colluded to ensure its sports stars were able to take a cocktail of banned performance-enhancing drugs yet evade doping tests, it has been revealed.

A 144-page report by the respected Canadian law professor Richard McLaren on behalf of the World Anti-Doping Agency (Wada) also found that more than 1,000 Russians athletes across more than 30 sports – including football – were involved in or benefited from state-sponsored doping between 2011 and 2015.

McLaren called it “a cover-up that operated on an unprecedented scale” – and pointed the finger at the Russian ministry of sport, the Russian security services, and the Russian anti-doping agency for creating what he called “an institutional conspiracy across summer, winter and Paralympic sports”.

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The International Olympic Committee (IOC) said that the findings showed “there was a fundamental attack on the integrity of the Olympic Games and in sport in general”. It announced it will examine all samples collected from Russian athletes during London 2012, following the findings in the report and will retest more than 250 doping samples from Russian athletes at the 2014 Sochi Winter Games.

Disturbingly McLaren warned that his report might only be the tip of the iceberg. “It is impossible to know just how deep and how far back this conspiracy goes,” he said. “For years, international sports competitions have unknowingly been hijacked by the Russians. Coaches and athletes have been playing on an uneven field. Sports fans and spectators have been deceived.”

McLaren put particular focus on Russia’s behaviour before London 2012, pointing out that many athletes were given a cocktail of undetectable steroids by the Russian Anti-Doping Agency before the Games – before being subjected to what he called “washout testing”, to ensure they did not test positive at the Olympics.

He said he had identified 15 Russian medal winners at London 2012 out of 78 participants on the washout list – 10 of whom had now had their medals stripped – but admitted he might have only scratched the surface.

“The results speak for themselves,” said McLaren. “The Russian team won 24 gold, 26 silver and 32 bronze medals. No Russian athlete was found positive for a prohibited substance during the Games and the testing at the time.

“Yet the Russian Olympic team corrupted the London Games on an unprecedented scale, the extent of which will probably never be fully established.”

This was the second and final part of McLaren’s investigation into Russian doping. His first report, published in July, focused on the extent of the state involvement and on confirming the reports made by Grigory Rodchenko, the former head of the Russian Anti-Doping Agency. This time he put much more meat on the bones, having subsequently conducted more interviews, and acquired more than 1,100 emails and documents and 4,000 Excel spreadsheets, many of which have subsequently been published on the website www.ipevidencedisclosurepackage.net.

He was also able to confirm how urine samples, which had been taken from Russian athletes at the 2014 Winter Olympics in Sochi and at other major championships, had been swapped for their clean urine by using small metal rods to prise open the supposedly tamper-proof bottles. They were carried out by the state security service, the FSB, with McLaren describing them as “magicians”.

Those clean samples were treated with salt and coffee to alter their consistency, tests on which showed in some cases that “samples had salt readings that were physiologically impossible”.

Facebook Twitter Pinterest Richard McLaren speaks during a press conference following the publication of his report on doping in Russian sport, at a hotel in central London. Photograph: Facundo Arrizabalaga/EPA

McLaren also revealed that at those Winter Games in Sochi:

• 12 Russian medallists were found to have had scratches and marks on the inside of the caps of their B sample bottles, indicating tampering.

• The winners of four gold medals, as well as a female silver medal winner, had physiologically impossible salt readings in their urine, evidence their samples had been tampered with.

• Two female ice hockey players had male DNA in their urine samples. This, said McLaren, provided “incontrovertible confirmation that the original samples had been swapped”.

However, McLaren refused to be drawn on whether Russia should have the 2018 World Cup taken away from them or be banned from the 2018 Winter Olympics. “My function was to be an investigator and to investigate facts,” he said. “It is up to the different parties, like the International Olympic Committee, to make their decision.”

Rod Carr, the chair of UK Sport, urged international sport to take strong steps to deal with Russia and suggested that the doping culture was such in the country that it would be unlikely to reform before the 2018 Winter Olympics in PyeongChang, in South Korea. “The report is truly shocking,” he said. “It’s unprecedented and deeply worrying for high-performance sport and I hope that both Wada and the IOC and the world sporting community has the processes and confidence to deal with this in the way that it should.

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“It would take a lot to persuade me that they could be totally rehabilitated in time for PyeongChang and have a new culture. When I hear senior people in the Russian sporting and political establishment deny a lot of stuff, every time that happens, I’m thinking it’s going to take longer than it could.”

Carr’s position was supported by Travis Tygart, the head of the United States Anti-Doping Agency, who urged the IOC to immediately suspend the Russian Olympic Committee. He said: “The IOC has to act – and clean athletes won’t be satisfied until Wada is empowered to be a truly independent global regulator and the Russian Olympic Committee is suspended. No international sporting events should be held in Russia until its anti-doping program is fully code compliant and all the individuals who participated in the corruption are held accountable.”

McLaren said he would make the evidence of each athlete’s wrongdoing available to individual sports federations – but it would be up to them to impose sanctions as they saw fit. He also appealed to the IOC and the world’s various anti-doping agencies to join together to end doping in sports.

“Over the past few months we have seen infighting between many different actors within international federations and among the anti-doping world,” he said. “I find it difficult to understand why we are not on the same team. We should all be working together to end doping in sports. My investigation has gone a long way to bringing this dark secret into the open. Now we must move forward and find solutions.”