Sister Lydia Allen, who told a royal commission she conducts psychological assessments at the Seminary of the Good Shepherd in Homebush, is under investigation by the Australian Health Practitioner Regulation Agency which oversees the registration of health professionals.

Only psychologists registered with the Psychology Board of Australia, which works in partnership with AHPRA, can use the title psychologist.

Sister Allen appeared before the Royal Commission into Institutional Responses to Child Sexual Abuse earlier this year where she was questioned about her role at the seminary, which is one of the largest in Australia with 50 seminarians.

She told the commission she conducted psychological assessments and counselling as part of a screening process for seminarians to determine whether they are suitable for religious life.

"I do an assessment process, which includes an interview, extended interview, and then I have them come in a few half days where they would do the testing," she told the commission's case study into Catholic Church authorities in February.

"Just stopping you there, are you describing psychological tests?" counsel assisting the commission Stephen Free asked.

"Psychological tests, yes, thank you," Sister Allen replied.

The assessment includes questions about sexual abuse, sexual identity and sexual orientation, the commission heard.

Sister Allen told the commission psychological testing was just one part of the screening process for seminarians.

"We do have a multifaceted system, although I am the psychologist and the buck stops here in that regard," she said.

According to the Seminary of the Good Shepherd's website, Sister Allen has a Ph.D in psychology and has practiced as a clinical psychologist in the US and Germany.

No one with the name Lydia Allen is registered as a psychologist with the Australian regulator.

AHPRA can commence a criminal prosecution in the course of an investigation, refer the complaint to the Psychology Board of Australia or determine no further action is warranted.

A spokeswoman for the Catholic Archdiocese of Sydney said Sr Lydia had international qualifications in psychology.

"The Archdiocese is investigating whether there has been some administrative oversight in relation to Sr Lydia's registration in Australia," she said.

"Irrespective of that, Sr Lydia has international qualifications in the field including a doctorate from the Fielding Institute in the USA and an advanced psychology degree from the University of Munich in Germany."

Meanwhile, the state government has announced plans to provide extra training to child protection workers to help them recognise and respond to children who have suffered sexual abuse or are at risk.

The NSW Department of Family and Community Services launched the resource on Wednesday.

Family and Community Services minister Pru Goward said children and young people are seven and a half times more likely than adults to be victims of sexual assault.

"It's essential that child protection workers understand the layers of risk that make some children more vulnerable than others," she said.