VANCOUVER - Vancouver police are defending their use of a Taser stun gun on a teenage mom, saying officers took the action to save the life of a critically ill one-month-old baby.

Const. Jana McGuinness said Friday that police negotiated with the "mentally distraught" 16-year-old mother for three hours and used the Taser because they were worried she might smother the little boy.

"Intervening was of paramount importance at that point to save the child's life," she said.

She said police were called to a home earlier this week when social workers were unable to convince the mom to hand over her child. The Ministry of Children and Family Development had issued an apprehension order because he needed medical attention.

McGuinness said the baby had been ill since birth but she couldn't reveal any details about his condition.

McGuinness said the mother was holding the baby but, at times, police worried she might smother him.

She said after the mother was hit with the shock weapon, she and the baby were taken to hospital and the mother was apprehended under the Mental Health Act.

McGuinness said the situation on Monday was "emotionally intense."

"At no time would one want to separate a mother from her child," she said. "It's the last thing we would want to do, anyone would want to do. And it was no doubt a traumatic incident for the mother."

Doreen Duncan, the baby's great-grandmother, said she's horrified about the incident, which came to light after the family spoke out.

"That is so disgusting," she said Friday. "I thought social workers and police were trained to deal with these things. I'm just so saddened by this."

Duncan said what bothers her the most is that the baby could have been hurt when police used the Taser.

"They could have missed. They could have Tasered him," she told The Canadian Press.

But McGuinness said the child was never in danger from the Taser because the stun gun was applied directly to the mother's upper back and arm.

The mother is distraught over missing her baby, said Duncan, who is the grandmother of the baby's father.

"The girl, she's missing the baby so much and they've always been together."

Duncan said the teen mom lives in a group home with her baby and social workers became concerned when the two failed to show up on Sunday night.

She said the pair, along with her grandson, were visiting her home the night before going shopping. When social workers called her looking for the teen, she assured social workers there wouldn't be any problem.

But she said social workers went to her grandson's home on Monday afternoon, where the Taser incident unfolded.

Police have come under intense scrutiny for using the shock weapons after a would-be Polish immigrant died at Vancouver International Airport last fall.

Robert Dziekanski was twice jolted by RCMP Tasers after the officers were called to deal with an agitated Dziekanski, who had been wandering around lost for hours after his flight arrived.

A report from a B.C. public inquiry prompted by his death is due later this year. A second phase of that inquiry, looking specifically into Dziekanski's death, is set to start in November.