Lyon (AFP) - The most senior French Catholic cleric to stand trial over one of the paedophilia scandals that have rocked the church denied in court Monday covering up for a priest who abused boy scouts in the 1980s and 90s.

Cardinal Philippe Barbarin, archbishop of Lyon, southeastern France, is accused along with five others from his diocese of failing to report a priest under his responsibility to the authorities.

The 68-year-old bishop, a conservative who has made headlines with his blunt comments in the past, denied the allegations which are the most damaging yet against the church in France.

"I never sought to hide, much less cover up these horrible acts," Barbarin told the court in Lyon.  

"I don't see what I'm guilty of," he added.

The Catholic Church has been roiled in recent years by claims against priests which have come to light in the wake of a global move by victims to go public with evidence.

Clerics have been denounced in countries as far afield as Australia, Brazil, Chile, Ireland, and the United States, leading Pope Francis to promise to rid the church of a scourge that has done enormous damage to its standing.

On Monday, the pontiff promised that the children on whom priests preyed would receive justice for what he termed "the vilest and most heinous crimes imaginable".

Barbarin said he confronted the accused priest, Bernard Preynat, about the abuse "rumours" in 2010 but let the matter drop after Preynat insisted he had changed.

In 2014, after meeting with one of the priest's victims, Barbarin contacted the Vatican about the affair but only removed the priest from his post a few months later after being told by the Holy See, he said, to delay awhile "to avoid a public scandal."

Barbarin has been accused of being deaf to the suffering of abuse victims before they went public.

He caused shock in 2016 by expressing relief that most of the claims over which Preynat was accused fell under the statute of limitations, meaning the abuse took too long ago for it to be investigated.

On Monday, he admitted that he had "not always used the best and most tactful words in the past".

He faces up to three years in prison and a fine of 45,000 euros ($54,000) if convicted of failing to report abuse of minors and failing to assist persons in danger.

'Stop same mistakes'

The scandal in Lyon first blew up in 2015 when former scout Francois Devaux went public with allegations that Preynat abused him as a child 25 years earlier.

Speaking shortly before the trial began Devaux said: "The goal is to stop the same mistakes being repeated."

Devaux filed an official complaint against Preynat in 2015 and against Barbarin the following year.

After six months of investigation and 10 hours of interviews with the cardinal, investigators dropped the case in 2016, saying the allegations against Barbarin, who has retained the support of the pope, were either too old or impossible to prove.

But nine victims succeeded in reopening the probe which led to Barbarin and others, including the now-archbishop of Auch and the bishop of Nevers in France, having to stand trial.

All of them worked in the Lyon diocese at the time of the abuse.

Vatican implicated

The victims' group, La Parole Liberee (Freed Speech), gathered testimony from a total of 85 people claiming to have been victims of Preynat in Lyon.

After he was first denounced in 1991, Preynat was prevented from leading scout groups, but he was later allowed to teach children and held positions of authority in parishes until 2015.

He has acknowledged abusing boys and is set to be tried later this year.

Two other French religious figures have been convicted of failing to report child abuse in the past: the archbishop of Bayeux-Lisieux, Pierre Rican, in 2001, and the former bishop of Orleans, Andre Fort, last year.

The head of the Vatican's powerful Congregation for the Doctrine of the Faith, Spanish Archbishop Luis Francisco Ladaria Ferrer, has also been accused of complicity in the alleged Lyon cover-up.

In correspondence with Barbarin about the priest, the Vatican's number three advised the cardinal to take "necessary disciplinary measures while avoiding public scandal".

The Vatican has cited his immunity from prosecution and he will not go on trial.