The global governing body of athletics is to abandon its policy of drug-testing every athlete during the upcoming world championships in Beijing, the Guardian has learned, with only a third of competitors slated to have their blood taken and scrutinised.

The decision to scale back on testing could be seen as a major public own goal by the International Association of Athletics Federations, given concerns about how widespread the problem of performance-enhancing substance abuse is in the sport.

The IAAF insists that it has simply introduced a better system that will target testing at elite athletes but its decision is causing consternation among competitors and teams. At the previous two world championships in Daegu in 2011 and Moscow in 2013 every athlete had a blood sample taken.

The move also comes against a backdrop of hugely damaging revelations for athletics which includes claims that a third of medals in endurance events at Olympics and world championships between 2001 and 2012, were won by athletes with suspicious blood values.

Last week 28 athletes from the 2005 and 2007 world championships were banned after their samples were tested, while on Monday the London 2012 Olympic 1500m champion Asli Cakir Alptekin was stripped of her gold medal and given an eight-year ban after abnormal values were found in her blood samples.

The revelations are likely to intensify the pressure on the International Association of Athletics Federations, which is due to elect either Seb Coe or Sergei Bubka as its new president in the early hours of Wednesday morning.

However, the IAAF told the Guardian it was not going soft on doping but had instead switched its focus to target testing around 600-700 specific athletes rather than mass screening the expected 1,900 competitors in Beijing. It also pointed out that its “core testing” for the world championships had started six months ago and that it was stepping up its use of more sophisticated testing methods in order to catch the cheats.

The IAAF had previously refused to reveal how many athletes it would test at the championships, claiming that “in order to maintain the integrity of the programme, the IAAF doesn’t disclose its actual testing programme for the event”. However, after confirming its approach to the Guardian the body moved to defend itself.

In a statement it said: “The most important time to be testing many of the athletes is during the off-season when the heavy training loads are taking place. That approach is no secret - but it is often easier for sports to simply pile on the tests during the event itself and claim a successful anti-doping programme.

“The reality is far from it. The testing in Beijing is important - but nowhere near as important as a truly non-notice out-of-competition (OOC) programme conducted during the preceding six months or longer.”

When asked specifically why the federation was scaling back on blood testing in Beijing, an IAAF spokesman said that in the previous championships it had collected a blood sample from every athlete because “it was establishing the athlete biological passport in athletics with a specific interest in establishing population-based reference values”.

“Another two years on, the passport is now well established and it has proved an effective tool not only for pursuing anti-doping rule violations but also as an intelligence source for the target testing of specific athletes,” he added. “The IAAF will be collecting between 600 and 700 blood samples at these championships and the majority of these will be targeted samples. The focus this time around will be on detection and elite athletes rather than deterrence and mass screening.”

But the IAAF’s explanation does not sit comfortably with everyone in the sport with concerns raised by leading coaches that the decision sent out a confusing and disappointing message. The fears are that focusing on detection rather than deterrence does not address the issues of doping among lower-level athletes and those coming up through the system.

It is also likely to raise a few eyebrows among fans after what has been a desperately damaging few weeks. Last week, the Sunday Times and ARD further claimed the London marathon was won seven times in 12 years by athletes with suspicious blood values, while the IAAF revealed that “adverse findings” emerged from retested samples from 28 athletes taken during the 2005 and 2007 world championships. The Sunday Times has also alleged that a successful British athlete was found to have suspicious blood values, although it has not named the person.

The IAAF has also come under heavy criticism. Last week the Olympic discus champion Robert Harting warned that he does not trust the federation, while Nick Willis, a silver medallist in the 1500m at the 2008 Olympics, said he feared that top athletes were protected "for the sake of the sport".

Insiders in the sport are also fearing the results of an ethics commission, headed by Michael Beloff QC, when it finishes its inquiry into potential corruption.

However, the IAAF maintains that despite all its recent troubles it is leading the way in global sport’s fight against doping. It hopes that its out-of-competition testing programme in the runup to Beijing, which started at the beginning of the year, will bear fruit.

It told the Guardian: “The out-of-competition testing has been intelligence-led, and specifically targeted based on known risk factors for doping.

“The IAAF also liaises closely with the various national anti-doping agencies to ensure that its own OOC testing is maximised, concentrating on filling the gaps where no effective national testing programmes exist. Other times that are just as important to test include, for example, the lead-up to the qualification events or when we know that athletes are chasing qualification marks/times.”

The IAAF also confirmed it would use the latest technology to catch more cheats using the blood booster EPO and human growth hormone (HGH) in Beijing. It added: “The IAAF is heavily utilising specialist analysis such as the IRMS (isotope-ratio mass spectrometry) test for EPO and HGH.

“While it is more expensive and at times harder to coordinate, it is crucial that as often as possible the tests are analysed for all possible banned substances, based on the risk factors for the relevant discipline.”

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