(CNN) If doping dominated the prelude to the Rio Olympics after the exclusion of a number of Russian athletes, it turns out drug testing protocols undertaken during the Games had "serious failings," according to the World Anti-Doping Agency.

So much so that on certain days, less than 50% of planned tests were carried out, with the report claiming out-of-competition targets for testing in the Olympic Village were "rarely met."

WADA criticized the lack of support and training given to the Rio 2016 chaperones, who were tasked with finding and informing the athletes they were required to undertake testing.

On several occasions, the report said, attempts to test athletes failed because more than half of the chaperones failed to turn up or arrived very late.

Often, other volunteers at venues across the Olympics had to be called on at the last minute in order to fill in for the chaperones, despite having no relevant experience or training.

"Chaperones were often provided with little or no whereabouts information for athletes targeted for Out-of-Competition testing in the Athletes Village," the report said.

"Therefore, the majority of times had to resort to asking team officials and/or athletes from the same team where the athletes they were looking for were located.

"Providing the names of the athletes they were seeking was (at best) highly inefficient and obviously compromised the 'no notice' nature of the testing."

'Mission aborted'

Due to these problems, the expected daily maximum of 350 urine samples was never collected. The most came on August 11 when 307 samples were collected, otherwise the busiest days fell between 200-250 samples.

"In addition, when initial attempts to find an athlete in his or her room were unsuccessful, chaperones often lacked the training and/or the confidence to follow up with further inquiries and effort to find the athlete in other locations in the Village (such as the dining hall)," it continued.

"Ultimately, many athletes targeted for testing in the Athletes Village simply could not be found and the mission had to be aborted."

Nonetheless, WADA president Craig Reedie said that he was pleased with some of the report's praise and "one or two significant improvements," but acknowledged the failings of sample collection.

"I'm disappointed in the criticism which is, if you look at the report, restricted almost entirely to the sample collection process," he told CNN's Alex Thomas.

"The IOC are in charge of all the anti-doping work at their Olympic Games, but they supervise the process and they ask the organizing committee to provide all the people to do all the work.

"A combination of financial issues and manpower issues meant that the sample collection business was not as efficient as it should have been."

Russian doping scandal

Headlines in the lead-up to Rio 2016 were dominated by Russian doping scandals after an independent study, the McLaren Report , revealed state-sponsored doping in the country.

Russia avoided a blanket ban from the Olympics, although only 271 of its athletes were cleared to compete.

Before the Olympic Games began, Alexander Zhukov, president of the Russian Olympics Committee, told reporters that no team has been drug tested as much as Russia. Earlier this month, Zhukov told Russian President Vladimir Putin he wanted to step down from his role.

FIFA vs. IOC

In the report, WADA said there were other aspects that it found "surprising."

For example, there was no out-of-competition tests conducted at all in football, while there was little or no in-competition blood testing in many high risk sports and disciplines, including weightlifting.

"I'd like to hear that they (FIFA) were ready to do it and for whatever reason it wasn't done," Reedie said. "Football was spread all around Brazil; it's a very, very big country as you know.

"Sometimes it starts even before the Games start and there were logistical problems in Brazil, there's no doubt about that and that's disappointing."

CNN asked FIFA directly about the lack of out-of-competition testing at Rio 2016 and soccer's governing body said the responsibility of testing at the Olympics is solely with the IOC.

"Prior to Rio 2016, FIFA conducted unannounced out-of-competition anti-doping controls and collected 57 urine and 57 blood samples," world football's governing body said.

"At the Olympic Games, however, the testing authority lies with the IOC."

'Outstanding legacy'

In total, 498 fewer tests were carried out than planned and over the course of the Games, 3,237 individual athletes were tested, 28.62% of the total participating.

However, the report did praise several members of dedicated staff as "without them, the Games anti-doping program would have almost certainly collapsed."

WADA also commended the Brazilian Doping Control Laboratory (BDCL), which responded to requirements prompted by the revelations made in the McLaren Report.

"The BDCL was superbly equipped, operated very securely and generally very efficiently," it said. "And now represents an outstanding legacy from the Games for the anti-doping movement in South America."

CNN reached out to the IOC to ask why it, rather than WADA, is responsible for delivering the anti-doping program for the Olympic Games, but is yet to receive a response.

Reedie also believes that any organization in charge of anti-doping at Rio 2016 would have struggled to achieve better results than the IOC.

"In retrospect, I think if anybody else had been in charge of the testing procedure they would have had the same logistical difficulties that appeared in Brazil."