An Australian victims advocacy group says an apology from the Pope and the leader of Ireland's Catholic Church will not be enough to help victims of church abuse.

Both the Pope and the leader of the Catholic Church in Ireland, Cardinal Sean Brady, have asked Irish Catholics for forgiveness over a sexual abuse scandal which began in the 1970s.

The apology to Irish Catholics follows similar expressions of remorse from the Pope to Catholics in the United States and Australia in 2008.

Chris MacIsaac from victims advocacy group Broken Rites says nothing much has changed since the Pope's apology.

"Broken Rites continually gets calls from people who tell us that the process set up by the church to deal with these matters is inadequate and certainly doesn't serve them well," she said.

"In fact, a lot tell us they're left worse off and feel psychologically abused by the process itself."

She says the church is still unable to find ways of making victims' complaints heard and properly handled.

Pope's pastoral letter

Speaking in English to pilgrims and tourists at the Vatican, Pope Benedict said he would sign his long-awaited pastoral letter dealing with paedophilia in Ireland.

"As you know, in recent months the church in Ireland has been severely shaken as a result of the child abuse crisis," he said.

"As a sign of my deep concern I have written a pastoral letter dealing with this painful situation. I ask all of you to read it for yourselves with an open heart and in a spirit of faith.

"My hope is that it will help in the process of repentance, healing and renewal."

The Pope has made no mention of other clerical abuse scandals that have in recent weeks rocked the Catholic Church in Germany as well as the Netherlands, Austria, Switzerland and Brazil.

In Germany, two-thirds of the country's dioceses have been implicated in physical and sexual abuse allegations made by more than 250 former students of Catholic institutions.

Speaking out for the first time, German Chancellor Angela Merkel called the scandal a major challenge to German society.

"I think that we all agree that sexual abuse of minors is a despicable crime and the only way for our society to come to terms with it is to look for the truth and find out everything that has happened," she said.

Cardinal's apology

At a St Patrick's Day mass in Armagh, Cardinal Brady expressed his regret for any failures on his part in connection with an investigation 35 years ago into abuses by a paedophile priest.

"I want to say to anyone who has been hurt by any failure on my part that I apologise to you with all my heart," he said.

Speaking later to journalists, Cardinal Brady said he was ashamed he had not always upheld the values he believed in.

"I apologised to those who have suffered as a result of abuse in the past, and particularly I apologised to those who due to my failures in the past have suffered," he said.

"Dealing with the past is never easy but it has to be done and the future has to be faced."

Cardinal Brady has so far resisted public pressure to resign for not informing police about the abuse and agreeing that the victims should remain silent.

With today's formal apology, some Catholic worshippers have given the Cardinal their support.

But Irish abuse victim Colm O'Gorman says Cardinal Brady has lost his moral authority.

"I'm afraid an admission of regret and statements of shame - whilst important - don't go far enough to acknowledging the significant responsibility that he has," Mr O'Gorman said.

Mr O'Gorman said he was left clinically depressed and suicidal following his experiences.

But he said the systematic cover-up of the abuse was the even greater crime.

"If an organisation constantly refuses or fails to put in place proper boundaries to contain the behaviour of offending priests, their behaviour will continue," he said.