The prison monitoring board has been ordered to investigate allegations by an ex-inmate that he was strapped to a chair for hours and refused water.

In the latest claim of abuse at the hands of prison authorities, the former prisoner said he was humiliated by the prison director Alex Dalli.

It was the first time anyone confined to the so-called 'punishment chair' had spoken up about their treatment.

In a statement, a spokesperson for Home Affairs Minister Byron Camilleri said that any inmate can report wrongdoing to an independent monitoring board.

"During his time in prison and even upon his release, the individual has every right and opportunity to report any cases of alleged wrongdoing to the Corradino Correctional Facility Monitoring Board which is an independent board tasked with investigating such claims," the spokesperson said.

"Upon being made aware of these claims, Minister Camilleri requested the Chairperson of the Corradino Correctional Facility Monitoring Board to investigate these allegations immediately."

The prison authorities deny the claims made by the prisoner in an interview with presenter and activist Peppi Azzopardi published on Wednesday.

"The Correctional Services Agency categorically denies these allegations," prison COO Randolph Spiteri told Times of Malta.

"The Agency reiterates its readiness to testify before any investigating body to present the appropriate evidence."

In the interview, the former inmate claimed that the incident happened when he was transferred from Mount Carmel's prison facility to Corradino.

He claimed that upon his arrival, Dalli asked him to hand over drugs, and when the inmate told him he had no drugs, he was strip-searched, taken to the doctor and given laxatives to defecate.

Afterwards, he said he was strapped to the restraint chair and humiliated for eight hours, during which he claimed the prison director circled him and taunted him to hand over drugs, even though no traces of drugs were found.

He also said he was refused water when he told them he was thirsty and that two prison warders, who tried to stick up for him were shut down by the prison chief.

The former prisoner is now asking to be called to testify about the incident and others at Corradino Correctional Facility before a three-person board that is investigating procedures at the prison.

In the meantime, psychiatrist Dr Anton Grech, who is heading the investigation board, said that he will take up the allegations with the board.