The inquiry also heard not a single staff member accused of abusing a child asylum seeker at Nauru has been charged with an offence, and conditions were so hot inside tents that young children fainted.

Former Save the Children worker Natasha Blucher was among a group of charity workers removed from Nauru amid now-debunked claims they encouraged detainees to harm themselves. She was joined at the inquiry by a colleague, Samantha Betts, who was not involved in those allegations.

Ms Betts said sanitary products were provided to women who were menstruating on an "as needed" basis and women were made to routinely ask male guards for the items each time they went to the toilet.

After questioning the practice, Ms Betts said she was told by guards it was necessary for "security reasons", because sanitary pads were allegedly soaked in petrol during 2013 riots at the centre.

Greens senator Sarah Hanson-Young told the inquiry there were no female detainees at the centre during those riots.

Ms Betts said temperatures inside school tents reached 50 degrees, causing children as young as five to faint. She said workers were told that reports of such incidents should be downgraded from "critical" to "minor".

Immigration officials later said the department would inquire into those allegations.

The former detention centre workers told the inquiry that detainees, including pregnant women and children, were often provided with ill-fitting clothes, sometimes held up with hair ties.

Ms Blucher said a case worker "once came into a tent holding a pair of pink hotpants, that had been provided to an elderly Burmese client of hers as shorts".

She said detainees were routinely referred to by their boat identification numbers, rather than their names.

Upon questioning this, she was allegedly told by security staff "we can't remember the names, all our paperwork only contains numbers".

Transfield Services, which runs the detention centre at Nauru, says there have been 67 child abuse allegations at the facility – 30 against staff.

The company's commercial and strategy manager, Erin O'Sullivan, said she was "unaware of any charges being laid" over the alleged staff incidents.

Transfield Services could not guarantee that the staff had been permanently dismissed from the detention centre.

It said the definition of child abuse was broad, and included children fighting and inappropriate discipline within families, as well as alleged abuse by staff.

The company is being paid $1.2 billion to run detention facilities at Nauru and Manus Island as part of the controversial offshore processing regime instigated by the former Labor government.

The contract expires at the end of October. Labor senator Kim Carr asked how the firm reconciled the serious allegations of abuse at Nauru with its commitment to upholding human rights at the facility.

Transfield Services also apologised to Ms Hanson-Young on Monday after security officers allegedly ran a secret surveillance operation on her when she visited Nauru in 2013.

At the time, Immigration Minister Peter Dutton dismissed the claims and called the senator "an embarrassment to our country".