Atlético Madrid have severed their relationship with the man who ran their youth system for 20 years and launched an investigation after he admitted to sexually abusing a boy in his charge at the Catholic boarding school where he lived and worked.

Friar Manuel Briñas, who is 88 and is known as the man who discovered Fernando Torres, told El País that it had happened “once, maybe twice” in the mid-1970s and that he “stopped immediately”, but his version does not tally with that of the victim and four other former students who have come forward with testimonies of abuse, according to the newspaper.

There have been no accusations from players at Atlético and, a club statement said, “no grounds for the slightest suspicion”, but they have begun an investigation. Atlético will also review their protocol for the protection of young players. The director of the school where Briñas worked expressed his “total shock” at the revelations.

Briñas admitted he had abused an individual names as Miguel MH, now aged 59, at the Hermanos Amorós school, where he had responsibility for sports and excursions. Miguel MH never told his parents but contacted Briñas in the last year in an attempt to “understand” and to “forgive”. He related how Briñas had assaulted him in a tent on a school camping trip to the Gredos mountains outside Madrid.

Confronted with the testimony, Briñas told El País: “I could never explain it.” He called it an “accident”, “strange things that happened back then” and he linked it to the death of the woman he was going to marry and his decision to then become a friar. He described his actions as a “thorn in my soul” and insisted it had happened “once, maybe twice”.

According to the testimony of Miguel MH, though, the abuse continued between 1973 and 1975 until he confronted Briñas – on one occasion slapping him as he approached in the dark, on the other demanding he turn back, having awoken to find himself in the back of the teacher’s car while other students slept by a lake. Four further victims have come forward with allegations of sexual abuse. One of them described Briñas’s actions as “an open secret”.