Celibacy cannot be blamed for clerical sex abuse because the average perpetrator does not commit the crime for up to 20 years after entering the priesthood, according to a top Vatican expert.

Professor Hans Zollner, a member of the Vatican's Commission for the Protection of Minors, said "celibacy as such is not the problem" because the average age of clerical paedophiles is 39. If were a problem, the age would be closer to that when priests take their vows, which is usually in their twenties.

The "biggest risk", he warned, was when "celibacy is not lived in an integrated way", and when priests are not given the support they need for their priesthood, which can lead to isolation, spiritual difficulties and even addictions.

Prof Zollner was giving an address to a symposium on the formation of Catholic priests at the national seminary in Maynooth, Co Kildare.

He stressed that greater attention must be given to the protection of minors and vulnerable people in the formation of seminarians, and that it must not be confined to a one-off safeguarding lecture or workshop so that a box could be ticked.

Highlighting a current campaign in the European Union which suggests that one-in-five people in Europe has been abused sexually, Dr Zollner asked how many men in Catholic seminaries had been victims of abuse.

"I believe that as a Church we have put away the trauma of sexual abuse," the 51-year-old said. He warned that more needed to be done to address the residual trauma of the abuse scandals.

Elsewhere in his address, he warned against prioritising quantity over quality in choosing candidates for the priesthood.

"There is an urgent need for more priests but do we lower our admission standards for that reason," he asked.

"When you take in anybody, the indirect effect is that it deters those who are up to the job and may not think of entering the seminary," he said.

He said this was because they saw weak individuals who have been accepted, and were put off by that.

He also hit out at bishops who disregarded seminary formators' advice on poor quality candidates, and push ahead with ordaining unsuitable men in order for them to look good on vocations numbers.