Immigration Minister Scott Morrison has defended limiting an asylum seeker's contact with her sick newborn, saying the baby is in hospital and it is "common practice" for mothers not to stay overnight.

The Rohingya woman from Myanmar gave birth by caesarean section last week to a baby boy who has since been kept in special care at Brisbane's Mater Hospital.

However, Fairfax news reports say the 31-year-old mother, called Latifar, was moved back into detention on Sunday, when her sick baby was just four days old.

She is currently being detained at an immigration centre in Brisbane with her husband and two other children, aged four and seven.

They had been held in the offshore processing centre on Nauru and are set to return there.

The baby was discharged from hospital on Thursday afternoon.

Mr Morrison's office has released a statement saying the mother has been able to see her baby during the day.

"The baby remains in a special care unit at Mater Hospital, Brisbane and the mother is being transported to the hospital daily," the statement said.

"She is able to, and has been staying with the baby throughout each day.

"Doctors at the hospital advise it is common practice for mothers not to stay overnight with babies in special care units due to bed restrictions."

Separation 'inhumane' and 'senselessly callous'

Opposition frontbencher and former health minister Tanya Plibersek says she does not know the specifics of the case, but says mothers and babies should not be separated.

"I think it's very important for mother and baby to be allowed to be together to bond," she said.

"Those early hours and days are critical for the health of the mother and the baby, including for things like establishing breastfeeding, which we know is the best possible start to give any baby."

Greens Senator Sarah Hanson-Young says the separation is unacceptable.

"Would we accept this for other people?" Ms Hanson-Young said.

"Would this be something that any of us would wish on our sisters, people's wives, on our own mothers?

"It is absolutely inhumane and senselessly callous."

A church group is also questioning why the woman is being prevented from staying with her baby.

Misha Coleman from the Australian Churches Refugee Taskforce says the mother is only allowed to visit her son between 10am and 4pm.

"This is a couple that had already been in a Malaysian refugee camp for 10 years," Ms Coleman said.

"They have kids who have no proper schooling and no future, and they've already had a tough decade.

"We as a Christian organisation are saying enough tough. It's time for compassion."