A spokesman for Immigration Minister Peter Dutton says claims by an Australian guard that asylum seekers at Nauru detention centre were water-boarded are "unsubstantiated" and the firm at the centre of the allegation strenuously denies the assertion.

The unnamed whistleblower, who works for Wilson Security, made the torture allegations in a submission to the parliamentary inquiry examining abuse at the centre.

He said asylum seekers were water-boarded and secured to metal frame beds that were thrown into the air so they crashed onto the floor.

In his submission the whistleblower also gave a detailed explanation of a technique called "zipping".

"This process occurs by using cable ties to secure an asylum seeker to a metal bed with metal bars at the base ... the bed is thrown into the air and injury caused to the asylum seeker as the bed strikes the floor," he said.

Wilson Security rejected the water-boarding and zipping claims and dismissed the submission as "inflammatory, incorrect and misleading" saying there was no evidence to support the allegations.

"There is not, and has never been, any suggestion that this has ever occurred - apart from this unparticularised and generalised claim," the company said in a submission to the inquiry.

"We are extremely concerned at the seriousness of the allegations in the submission. Of equal concern is the absence of evidence that supports the allegations - which is of particular concern in light of how serious they are. You will see in our response that we are able to reject many of the claims convincingly, with supporting documented facts," the submission said.

"However, in other cases we are dealing with unparticularised and generalised assertions with no detail. It is difficult to respond to such matters."

The company said a complaints process existed in which asylum seekers could disclose incidents of abuse, but there had been no complaints about the alleged water-boarding.

It also said asylum seekers have regular access to telephone, internet, and social media, and yet no claims had emerged.

Wilson Security urged the parliamentary committee not to make the submission public because it could cause "significant distress, consternation and agitation at the centre, and compromise the safety of people there".

Companies 'strongly reject claims'

A spokesman for Immigration Minister Peter Dutton said no claims of water-boarding had been made to the Government or brought to its attention.

"The submission to the Senate Committee makes numerous, unsubstantiated assertions," the spokesman said.

"The Government notes that both service providers to the Nauru Regional Processing Centre – reputable major companies - have strongly rejected the claims made in the submission."

The submission by the whistleblower also alleges guards regularly goaded asylum seekers into reacting and then bashed them, but the company denied there was a "random cycle of abuse".

The guard accused his employer of regularly shredding incriminating documents, a claim the security firm also denied.

He said Wilson Security staff bashed a male refugee senseless following an incident at the Jules nightclub in Nauru and the refugee was later thrown from the club's balcony.

The refugee had allegedly touched a female aid worker inappropriately, he said.

The company's version of events is that the intoxicated refugee was removed from the venue after sexually assaulting the female worker, who did not wish to press charges.

The refugee returned later with two companions and confronted staff who had removed him.

"They defended themselves and there was a resulting altercation," the company said, adding there were no serious injuries and the police were not called.

The guard claims Wilson Security staff are heavily comprised of former Australian and New Zealand soldiers who harbour ill will towards people from countries where they served.

"Many Wilson Security staff fought against the asylum seekers they are now guarding," he said.

The company said it employs a diverse workforce and provides continuing cultural awareness training.

The guard also said staff were given no training on how to deal with detainees' mental health issues.

"Rather, asylum seekers were simply cast as criminals from the start," he said.

The company insisted its training was up to scratch and staff are required to treat asylum seekers with respect and dignity based on a code of conduct.

The whistleblower also alleged "Wilson Security forced asylum seekers to provide statements that certain other asylum seekers were rioting but these 'informers' were not on Nauru at the time of the riot".

AAP/ABC