The former President Mary McAleese has hit out at Pope Francis, who said it is OK to slap children who misbehave.

The Pontiff told a crowd at the Vatican that he met a father who said he hit his children if they behaved badly.

Pope Francis said the man was right to administer punishment - but never to hit a child in the face.

Mrs McAleese has warned this could signal a 'turning back of the clock' in the attitude of the Catholic church to corporal punishment and children's rights.

In a letter to the Irish Independent, Mrs McAleese - who is now in a senior academic post at St Mary's University in London - highlights that the Vatican is a signatory to the UN Convention on the Rights of the Child.

"Is the Holy See now doing what it claimed not to be doing a year ago, namely actively and internationally promoting the corporal punishment of children," she writes. "If it is, then Pope Francis has surely turned the clock back considerably."

The UN Committee said the Vatican has not enacted guidelines banning corporal punishment of children in Catholic schools, as well as in the home.

In response to the Pope's comments, Mrs McAleese says: "What faith are we to have now in the Holy See's commitment to the Convention on the Rights of the Child?".

In her letter, she questions whether the Pontiff's "recent advocacy of parental corporal punishment of children (provided it does not involve face-slapping apparently)" is an indication that the Vatican has "conducted the thorough study and investigation it promised the Committee on the Rights of the Child".

In a Newstalk poll held yesterday 69% of people said it is acceptable to slap a child, while 31% said it is not.