'Humanitarian duty': Australian doctor denies he was brainwashed into joining ISIL

The Australian doctor who fled to Syria to join the terror group ISIL has reportedly defended his actions as part of his "humanitarian duty" in a strident letter.

Adelaide University graduate Tareq Kamleh appeared in a recent ISIL-produced video urging other medical professionals to join the extremist group.

After his identity was revealed, former co-workers called him a "narcissist" and "pretty boy".

Now, Kamleh - who calls himself Abu Yousef al-Australie - has hit back in a letter, News Corp has reported.

Kamleh called his critics hypocrites, claiming "womanising or alcoholic behaviours" were prevalent in all Australian medical schools.

"I formally deny that I have ever taken part in unprofessional conduct which would have jeopardised my doctor-patient relationship," he said.

He also denied he had not been brainwashed into joining ISIL, calling his decision "educated and calculated".

"I have come here as there are locals suffering from normal medical conditions despite being surrounded by war, with an overt lack of qualified medical care," he said.

"Is it not my humanitarian duty to help these children also, or only kids with white skin and blue passports?"

He denied any involvement with the group's terrorist and murderous acts, but refused to condemn them.

"If they are correct I wish them progression, if they are not, this is between them and God," he wrote.