Anti-doping officials in Russia are being stopped from testing athletes and threatened by security services, says a World Anti-Doping Agency report.
The report was published two days before athletics' governing body rules on whether Russian competitors can take part in the Rio Olympics this summer.
In November, Russia's athletes were banned after a Wada report highlighted widespread failing in testing.
The country's athletics chiefs had pledged to make wholesale changes.
What does the Wada report say?
The latest Wada findings include:
73 of 455 tests on athletes could not be collected
736 tests were declined or cancelled
23 missed tests, which the report described as a "significant amount"
52 adverse findings
The report includes examples of the lengths athletes from different sports allegedly went to both to avoid tests and fool doping control officers (DCOs).
It says one athlete was seen running away from the mixed zone after an event, and another left the stadium during a race and could not be located.
Wada also highlighted the case of an athlete who, it says, used a container inserted inside her "presumably containing clean urine".
When she tried to use the container it leaked onto the floor and not into the collection vessel. The athlete is alleged to have tried to bribe the DCO before providing a sample that subsequently returned an adverse finding.
Other examples include:
DCOs intimidated when accessing military cities, and armed federal security agents threatening DCOs with expulsion from the country
Wada-accredited laboratories reporting sample transportation packages being opened by Russian customs, suggesting interference by officials
National championships for Olympic sports including Olympic qualifiers held in cities with restricted access due to ongoing civil conflicts resulting in service providers declining test requests. As a result, tests were not carried out at the national weightlifting and national Greco-Roman wrestling championships. In some cases, testers would not be told which city or venue an event was taking place in.
Russia threatens legal action
Russian sports minister Vitaly Mutko said the country could take legal action if its athletics federation is not reinstated to the International Association of Athletics Federations (IAAF), Interfax news agency reported on Wednesday.
"It seems to me it is necessary to start treating it from a legal point of view," he was quoted as saying. "I do not rule out that we will do this in the nearest future."
Meanwhile, Russian Olympic medallists and world champions have appealed to the head of the International Olympic Committee to let their athletes with no history of doping compete at Rio 2016.
"The fraud of dishonest people should not jeopardise the career of innocent fellow athletes," said 13 sports stars in a letter to Thomas Bach.
The 13 include Alexander Popov, a four-time Olympic champion swimmer, and judo champion Tagir Khaibulaev.
The IAAF, athletics' governing body, voted to suspend Russia's athletics federation (Araf) on 13 November after an independent Wada report alleged "state-sponsored doping".
The report was commissioned to investigate claims made in a documentary shown by German broadcaster ARD in 2014. The programme alleged widespread doping in Russian athletics — saying as many as 99% had cheated.
The claims were made by whistleblowers including Vitaly Stepanov — a former Russian Anti-Doping Agency official — and his wife Yulia (nee Rusanova), a former 800m runner who was banned for doping.
Russian athletes, including former London Marathon winner Liliya Shobukhova, also admitted to taking drugs and observing corruption.
The Wada report found evidence of state involvement, as well as destruction of samples, interference with doping controls, and payment of bribes to conceal positive tests.
Dan Roan inside Moscow drug-testing lab
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What happens next?
The IAAF outlined a number of conditions for Russian athletics to meet for the ban to be lifted. In announcing those conditions in November, IAAF president Lord Coe said: "Russia must demonstrate verifiable change across a range of criteria and satisfy our taskforce that those criteria will be met permanently."
He said he wanted to see "verifiable change both in anti-doping practice and culture".
The IAAF's council meets on 17 June in Vienna, where it will discuss what Russian authorities have done to tackle doping — and whether its athletes should be allowed to compete in Rio.
The Olympic athletics programme begins in Brazil on 12 August.