The Catholic Church in Australia on Monday apologised for the forced adoption of babies from young, unwed mothers in the 1950s, '60s and '70s, saying the practice was "deeply regrettable".

"We acknowledge the pain of separation and loss felt then and felt now by the mothers, fathers, children, families and others involved in the practices of the time," the apology said.

"For this pain we are genuinely sorry," said the statement from Catholic Health Australia and Sisters of Mercy nuns from Singleton, north of Sydney, in response to accounts of babies taken from their mothers in decades past.

Catholic Health, the representative body for Catholic Church-run hospitals and aged care services in Australia, said it had no way of knowing how many people had been affected by forced adoptions.

It said that over the past 20 years, people had come forward to speak about unacceptable adoption practices which it said were "regrettably common in many maternity hospitals across Australia" at the time.

"These practices of the past are no longer tolerated, nor allowed by today's law, and are deeply regrettable," the statement said.

The church said it agreed with a New South Wales state Parliamentary Inquiry into forced adoption which in 2000 found past practices were misguided, and at times unethical or unlawful.

At that inquiry, representatives of Catholic adoption services apologised for the practices of that era and the pain they caused.

A federal parliamentary inquiry is also probing the issue and has already received more than 300 submissions, many of them personal accounts detailing how babies were taken against their mothers' will.

Some women were pressured, deceived or threatened to ensure they signed away their rights to their children, according to submissions to the inquiry relating to births from the 1950s to as late as 1987.

Juliette Clough told state broadcaster ABC that said she was 16 when she gave birth to a baby, which she was forced to give up, in a Catholic hospital in 1970.

"My ankles were strapped to the bed, they were in stirrups and I was gassed, I had plenty of gas and they just snatched away the baby," she said.

"You weren't allowed to see him or touch him, anything like that, or hold him and it was just like a piece of my soul had died and it's still dead."

Catholic Health said it would offer support to anyone suffering as a result of past adoption practices, including help in accessing medical and adoption records and counselling.