A group of 34 women and children linked to Australians who travelled to the Middle East to fight for IS has been trying to travel home from a Syrian refugee camp.
Opposition Leader Angus Taylor said children should not be separated from their parents, but concerns still remained on whether they had been radicalised.
"It is truly tragic that we've seen people take children over to what is an ideological movement that promotes violence against innocent people," he told reporters in Melbourne on Friday.
Home Affairs Minister Tony Burke has confirmed the women have been issued with Australian passports - generally a right held by all citizens.
"It is tragic that children are involved .... there's real questions then about radicalisation and what might have occurred with these children."
The group is believed to be made up of the partners and children of Australian men who travelled to the Middle East to fight for ISIS, before the caliphate was toppled in 2019.
Senior Labor minister Tanya Plibersek delivered some of the strongest criticism yet of the women.
"Taking children into a war zone like this is child abuse," she told reporters in Melbourne.
"It is important to understand the responsibility that these parents took in making this decision."
A spokesman for the Department of Foreign Affairs and Trade said it was seeking further details with overseas authorities about the transferring of prisoners.
But additional powers should have been used to reject the the women's passport applications, Mr Taylor said.
"There are powers to refuse passports, and the government has not answered the most basic questions about why those things are not being used, or to what extent they have sought to use them," he said.
A two-year ban on entering Australia has been imposed on one of the women because of national security concerns, and government officials have said the group could face criminal charges if they return home.
The government has repeatedly claimed it is not providing any assistance to the women and children, apart from its legal obligation to give them travel documents.
Asked about the opposition's demand to deny the group passports, senior minister Mark Butler said while the government was open to suggestions on how to deal with the situation, the provision could only be used in certain circumstances.
"The grounds are very specific and they're very tight and they're determined ultimately by our national security agencies," he told Seven's Sunrise program.
"I'm sure Angus Taylor knows that there are very strict constitutional limits on what any government, Labor or Liberal, is able to do in the area of citizenship and passports," Mr Butler said.
