A paedophile priest who abused seven children, including altar boys, over a 34-year period has been jailed for 15 years.

"Predatory" Francis Paul Cullen, 85, pleaded guilty to 21 charges of indecent assault and other sexual offences last month after being extradited to the UK last year following 22 years on the run in Tenerife. The offences were committed between 1957 and 1991 on children aged between six and 14.

Cullen looked down in the dock at Derby crown court as sentence was passed on Monday. Judge Jonathan Gosling told the former clergyman: "You took full advantage of your position, and the trust in which you were held, to satisfy your perverted lust.

"It is impossible to reconcile the fact that you were administering the sacraments of the Catholic church – baptism, confession, communion, confirmation – at the same time as you were indulging yourself with these children, some of whom served you on the altar at which you celebrated.

"To say that you were a disgrace to your cloth understates your activity. This was gross hypocrisy. In a sentence, your entire life was a lie."

Dublin-born Cullen was traced to Tenerife last year with the help of the Catholic church's safeguarding board. He was extradited back to the UK on a European arrest warrant containing a series of sexual abuse charges.

The clergyman was due to deny the charges at Derby crown court last month but changed his plea to guilty on what would have been the first day of his trial.

He admitted 15 counts of indecent assault, five of indecency with a child and one of attempted buggery.

The crimes, committed against five altar boys and two young girls whose relatives had connections with the Catholic church, took place while Cullen was a serving priest in Mackworth and Buxton, both Derbyshire, and Hyson Green in Nottingham.

Four altar boys were abused while Cullen was practising in Mackworth, Derbyshire, between the 1950s and 1970s. In the 1980s, he abused two girls after he moved to work in Buxton, Derbyshire, and then went on to abuse another altar boy in the early 1990s after he moved to Nottinghamshire. The clergyman fled to Tenerife in 1991 while facing charges of sexual assault brought by Nottinghamshire police.

Prosecutor Sarah Knight told the court that Cullen had been a "well-liked and respected" clergyman whom families trusted and children "idolised". They were unaware of the "predatory paedophile" lurking behind the mask, Knight told the court.

She said his ministry in the Catholic church had been "a lie" that he used to abuse boys and girls in his pastoral care. The court heard that many of the altar boys were invited to have tea and cake with Cullen at his home where he then abused them. Others were attacked after mass or in his caravan on Cub Scout trips that he ran. Cullen even travelled to Ireland to visit one victim while he was on holiday, the court heard.

The judge said: "You were also welcomed into the parents' homes. They could never have guessed that in truth you were a predatory paedophile – a term which was at that time unknown to the vocabulary. You were, in reality, cunning, devious, arrogant – in the word of one of your victims, despicable."