The disgraced paedophile bishop Peter Ball stood in for his twin brother, also a bishop, on a number of occasions, the Church of England has admitted.
Ball resigned as Bishop of Gloucester in 1993 after he received a police caution for gross indecency. It has now emerged he replaced his identical twin Michael, then Bishop of Truro, at services and official duties on an unknown number occasions in the 1990s.
The current Bishop of Truro, Tim Thornton, said there are "one of two bits of evidence" which show Bishop Peter carried out duties that should have been performed by Bishop Michael.
"It might be that Bishop Peter thought it was clear that he was being Bishop Peter, and on some occasions might have made it very clear at the beginning that he was there in place of his brother, but it might not have been evident to everybody," Thornton told BBC Radio Cornwall.
The Diocese of Truro has appealed for information from churchgoers to investigate what happened when the two men were together in Cornwall between 1993 and 1997.
Thornton said if he had held service it would been a "limited number".
However a spokesman from the Diocese of Truro confirmed Peter Ball was granted "Permission to Officiate" within the Diocese of Truro in 1995 by the then Archbishop of Canterbury, Lord Carey.
The spokesman said: "There was an initial permission granted for a period of six months from March 1st, 1995, and then this was then extended by three years from September 1st, 1995."
Ball, now 84, was convicted of sex abuse against a string of young men who came to him for spiritual guidance. He was jailed for 32 months after a trial in October.
An independent inquiry is currently investigating whether there was a deliberate cover up of Ball's crimes, which were carried out between 1977 and 1992 while he was Bishop of Lewes. When a police investigation discovered his abuses in 1993, he was not prosecuted but was just given a warning and resigned.
It has since been revealed that while the investigation was ongoing, police and prosecuters received a number of letters of support from George Carey, as well as from MPs, a High Court judge and members of the royal family.