Confusion surrounds the issue of performance-enhancing drugs, with anti-doping authorities unable to clarify whether substances are banned or not, according to a Four Corners program to go to air on Monday night.

The Australian Sports Anti-Doping Authority (ASADA) is investigating 31 NRL players and the Essendon and Melbourne AFL clubs into allegations of potential abuse of anti-drug codes through the use of supplements including peptides.

Reporter Geoff Thompson told ABC News Breakfast that after months of research for the story, it was still unclear how widespread the use of performance-enhancing drugs were in Australian sport.

"A lot of these new products are simply in a grey area," he said.

"We've had requests in with ASADA to determine the status of a number of products that seem to be at the centre of this inquiry, and they still cannot tell us if they are absolutely banned or not.

"So if ASADA can't tell you that, what sort of hope does a young football player, for instance, have?"

Thompson said that substances could be banned for a number of reasons, including that they were performance enhancing, or that they had not yet been approved for human use.

"A lot of these things are up in the air, and I think that's the problem ASADA is going to have in all this," he said.

"Even if the players were taking this stuff, let alone the difficulty in proving that they were, establishing whether it (the substance) is banned at all is going to be a big hurdle for them to cross."

The program spoke to Shane Charter, the sports biochemist who has claimed that underworld figures tried to get him to spike players' supplements with cocaine to provide an opportunity for blackmail.

Charter has also said that he helped sportspeople from various sports to avoid positive drug tests.

Former Australian cyclist Dean Jones told the program that he had taken the performance-enhancing drug EPO during his career.

"I did a course of EPO, I had borrowed some money from my family and I didn't tell them what it was for," Jones said.

"I thought 'this is my last shot' and I bought some (EPO) and it was known through my doctor that you had to take iron to strengthen the new cells.

"So I bought some iron while I was in Germany, didn't read the packaging properly and I was injecting intravenously iron into my body.

"My vision started to go and everything, my heart rate accelerated."

Four Corners' program dealing with drugs in sport, "Who's Cheating Whom?", will be broadcast on ABC 1 tonight at 8.30pm AEST.