The offending comments were made during a discussion on the government's proposed needle and syringe program with host Mark Parton on 2CC's Breakfast Show last week.

"If you want to talk about the drug issue, I'm going to make a statement now that you're not going to like and a couple of people out there aren't going to like," Mr Gardner said.

"The prison guards should look at themselves, that's how the drugs are getting into the prison, you know it, and I know it, and the guards know it," he said.

Mr Gardner, who was arguing in support of a prison-based needle exchange, went on to say guards had been smuggling drugs into prisons for "eons".

"How else do the drugs get into the prison, Mark [Parton]? What do they just fly over the wall do they?" he said.

"Before the guards want to start whinging about the 22 people who might get a syringe, maybe they want to have a look at their own ranks to find out how the drugs are getting in there in the first place."

The comments have angered guards, who yesterday sent a letter signed by hundreds of corrections officers demanding the shock jock either produce evidence to back up his allegations, or publicly apologise.

Community and Public Sector Union regional director Vince McDevitt said his members were "appalled and angry".

Delegates have also invited Mr Gardner to their next union meeting to further explain his comments.

"They've all just been called drug smugglers and drug dealers, and they're law enforcement officers, it doesn't sit well with them," Mr McDevitt said.

The union recently passed a motion stating it would not support any guard involved in the illegal smuggling of drugs.

Capital Radio Network management have declined to comment, saying they are yet to receive a formal complaint, but will investigate the matter fully if one is received.

The comments come just two months after Mr Gardner was banned from the airwaves for disparaging comments about upskirting Prime Minister Julia Gillard.

He was kicked off air in June after joking Communications Minister Stephen Conroy should wear a "penis cam" to film up the skirt of Ms Gillard.