MELBOURNE coach Simon Goodwin says he was surprised by allegations of secret drug testing being conducted to enable players to avoid detection on game day.

Federal independent MP Andrew Wilkie told parliament on Tuesday night of the allegations made by former Demons club doctor Zeeshan Arain, ex-club president Glen Bartlett and Shaun Smith, father of Melbourne player Joel Smith, who is under investigation by Sports Integrity Australia after returning a positive game-day test for cocaine.

Wilkie said the trio had alleged players who tested positive had faked injuries and withdrawn from games to avoid match-day drug testing by Sports Integrity Australia (SIA), and that details of the "off-the-books" tests were never shared with SIA or the World Anti-Doping Agency (WADA).

On Wednesday morning, Demons premiership coach Goodwin insisted he had no knowledge of the alleged practice.

"(The drugs) policy is an AFL policy, it's an AFLPA (Players Association) policy and it's led through a medical model," Goodwin said.

"So you're asking me questions that I have no line of sight over. It's something that I've never really thought about.

"I just back in the process of what the policy is. These are questions you're going to have to ask the AFL."

League chief executive Andrew Dillon is expected to address the allegations on Wednesday.

Goodwin said the allegations would not make him second-guess the information he receives from club doctors.

"When you start to digest the information that you get given, you take it on face value," he said.

"This is a process that the AFL, the AFLPA and the club doctors put together from a confidentiality perspective, so to have no line of sight is not unusual.

"But I've got enormous trust in our doctor, in terms of them being able to do their job.

"I'm not going to question how they go about their business."

Wilkie described the allegations made by Arain, Bartlett and Smith as credible and detailed, and provided signed statements given to him clearly identifying the sources of the documents.

Wilkie said Arain alleged it wasn't a Melbourne problem but an "AFL problem" with a number of players arriving at the club with pre-existing cocaine dependencies.

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