A senior nun has spoken out for the first time about priests sexually abusing nuns in staunchly Catholic Poland following an unprecedented public admission by Pope Francis.

Mother Superior Joanna Olech was speaking after the pontiff earlier this month admitted that priest have used nuns as "sexual slaves" and may still be doing so.

She said: "The problem of sexual abuse committed by priests against nuns has also existed in Poland for a long time,"

 Ms Olech, who was the secretary general of women's religious orders in Poland between 1995-2008, was speaking to Poland's KAI Catholic news agency.

She said that in one of several cases she has seen, "a young nun who became pregnant, was forced to leave her order, but the father of the child is still a priest and certainly has not suffered any consequences for his actions."

"These cases have never been made public", even after being reported to the superiors of priests responsible for sexual abuse, she said.

She added that the scale of the abuse in Poland was unclear as "no studies have been done".

Sexually abused nuns have nowhere to turn, said Ms Olech, who has spent the last 50 years in a religious order.

But she also insisted that the "era when this problem has been swept under the rug is drawing to an end".

"Times have changed, perhaps the new generation of nuns will approach these issues in a different way," she added.

Some 18,000 nuns served in around 100 Catholic women's religious orders in Poland as of 2016, according to the Statistical Institute of the Catholic Church of Poland.

Catholic bishops from across the globe gather at the Vatican this week for a summit called by Pope Frances focused on tackling the wave of child sex abuse scandals assailing the Catholic Church.

The Polish episcopate insists it has "zero tolerance" for these criminal acts.

It has vowed to publish statistics on the number of child victims of priestly sex abuse, covering the period starting in 1989, when communism fell.