A paedophile priest fled the country after a police officer tipped off the Catholic Church in Birmingham, a sex abuse victim has claimed.
The man said the officer passed on documents about 30 years ago which led to James Robinson being "spirited away" overseas. The priest was later jailed.
The Archdiocese of Birmingham has always denied knowingly covering up the activities of paedophile priests.
West Midlands Police said claims about the officer were being looked into.
The anonymous victim, known as "Donald", was brought up in the Father Hudson Home for orphans in Coleshill, Warwickshire, where he was repeatedly abused by Father Eric Taylor, who was jailed in 1998.
BBC Midlands Today correspondent Peter Wilson said: "Robinson was Taylor's protégé, a Roman Catholic priest working across the West Midlands and Staffordshire. He was a serial child abuser.
"In 1985 he moved to America. Donald campaigned for his extradition."
In 2010, a year after being extradited, Robinson was jailed for 21 years for sexually abusing boys in the West Midlands between 1959 and 1983.
'Same as Rotherham'
Donald claims a police officer undermined the original investigation into Robinson.
He said the officer passed on a victim statement "prior to the arrest of James Robinson to the Catholic Archdiocese of Birmingham and subsequently Robinson was spirited away, first to Ireland and then to America, given a stipend and simply told to stay out of the way".
Donald said West Midlands Police should also investigate the actions of the church.
He said: "Given the fact that most of these priests were serial abusers why was it that the church kept on moving them from one parish to another hiding them?
"What we have here is the same thing that happened in Rotherham where those in power and in authority simply failed in their duty of care."
West Midlands Police said it had received a complaint concerning investigations into historical child sexual abuse in Birmingham, containing two allegations.
Ch Insp Dean Hatton from the force's Professional Standards Department said: "The second allegation claims an inappropriate disclosure was made to a third party during the initial stages of an investigation into former priest Richard James Robinson, jailed in 2010 for a string of sexual offences against boys.
"The Independent Police Complaints Commission has been made aware of the complaint and the matter was referred back to the force's Professional Standards Department (PSD) to investigate.
"This is not a criminal investigation but should any offences come to light during the PSD inquiry, then these will of course be investigated and appropriate action taken."
Mr Hatton said the other allegation related to concerns about the outcome of a previous complaint "into the force's handling of an investigation into alleged abuse by members of the Catholic Church".
"Following advice from the Crown Prosecution Service and careful consideration by West Midlands Police, it was decided no further action should be taken in respect of the original investigation."
Jane Jones, safeguarding co-ordinator for the Archdiocese, said changes had been made to ensure such offences were reported to police.
"James Robinson may have been moved for the wrong reasons, I'm not in a position to comment on that. But if there are concerns in a parish now everyone has access to my phone number," she said.
"Clergy are trained differently everybody is made aware of what should happen and aware of how these things arise and what to look out for.
"We have a good system in place now."
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