Allegations of 33 cases of sexual abuse involving children in detention centres in Australia have emerged.

Immigration department figures obtained by Fairfax Media show that there were 33 cases of alleged sexual assault involving children in Australian detention centres and Christmas Island between January 2013 and March 2014. The figures do not extend to Nauru or Manus.

Asylum seekers at Nauru detention centre. A worker at the controversial centre told Fairfax Media that she often saw children sitting on guards' laps late at night. Credit:Angela Wylie

The figures follow allegations of sexual abuse of women and children on Nauru, including underage asylum seekers being forced to perform sexual acts in front of guards; female asylum seekers being told to strip naked in front of guards if they wanted a shower longer than two minutes; and one woman being told she would be raped if she was resettled in the Nauruan community.

On Tuesday, Immigration Minister Scott Morrison broke his silence on the Nauru allegations, saying they were of a "generalised nature" and that he had referred them to his department.