Human rights group Amnesty International is calling for an independent inquiry into the tear-gassing of six teenagers in Darwin's juvenile detention centre last month.

The boys - aged between 14 and 17 - were tear-gassed last month and a member of the dog squad was called in to help subdue them, after they damaged a cell block, armed themselves with broken glass and confronted prison officers at Don Dale Juvenile Detention Centre.

Amnesty International's Indigenous Rights Adviser Rodney Dillon says it was a shocking and cruel decision to use tear gas and the circumstances surrounding it need to be examined.

"This is extreme to get to this stage where you've got to put tear gas on kids," Mr Dillon said.

"There's got to be stages leading up to this and that's what we're saying - there needs to be an inquiry as to why it got to this stage."

Soon after the children were tear-gassed, Correctional Services Commissioner Ken Middlebrook defended its use.

He said the young people were given a number of directions to lay down their weapons and lie on the floor, which they refused to do, and one barricaded an exit.

"I gave the order to deploy a short quantity of gas, which certainly distracted him long enough for the officers to move in and remove him and the other detainees," Mr Middlebrook said.

"It was, I felt the only option," he said.

But Mr Dillon has called for an inquiry that is independent of Correctional Services, saying that the children involved must have had reasons for their actions.

"The kids don't get up in the morning and say 'we are going to destroy everything here today'," he said.

He said that if Australia had ratified the Optional Protocol to the Convention Against Torture (OPCAT), the detention centre may not have been able to use tear gas on children.

Australia became a party to OPCAT in May 2009, but has not yet ratified the agreement.

"Who gave the permission to use tear gas on kids and is that what we want to be seen to be doing in this country?" Mr Dillon asked.

He said tear gas was not used anywhere else in Australia and questioned why it was used in the Northern Territory.

Mr Dillon also questioned putting children from the Don Dale centre into the adult prison at Berrimah, which has been occurring since a new adult prison opened recently.

"This prison wasn't good enough for adult prisoners, so we are going to spend $800,000 on it, put some paint on it and it will be good enough for kids?" he said.