(CNN) -- The Czech Republic's practice of surgically castrating convicted sex offenders is "invasive, irreversible and mutilating" and should stop immediately, the Council of Europe's Anti-Torture Committee said in a report made public Thursday.

The central European country castrated at least 94 prisoners in the 10 years up to April 2008, when investigators from the Council of Europe, a human-rights forum, visited the Czech Republic.

The Council of Europe condemned the practice as "degrading."

The procedure is being performed even on first-time, non-violent offenders, such as exhibitionists, its investigation revealed.

Prisoners have to request castration under Czech law, but many fear they will be jailed for life if they do not, the investigation found.

"In practically all the cases, these patients indicated that their application was at least partially instigated by fear of long-term detention," the report said.

"Some patients claimed that the treating sexologist had explicitly told them that surgical castration was the only available option to them and that refusal would mean lifelong detention."

And it warned that some "significantly" mentally retarded people had been castrated.

"In at least five cases, legally incapacitated offenders were surgically castrated," the report said. "In all of these instances, the court-appointed guardian had signed the consent form; in two cases, the guardians were mayors."

The investigators found only two convicts who had spontaneously volunteered for castration, while others they interviewed said mental health staff specializing in sexuality had recommended it.

"The other patients interviewed indicated that the treating sexologist had suggested surgical castration, in several cases within a week of the patient's admission to hospital," the report said.

"Some of the sexologists interviewed by the delegation themselves affirmed that for certain patients there was no alternative treatment to surgical castration."

The Czech Republic defends the practice as voluntary, saying castration aims permanently to reduce testosterone levels in order to diminish the offender's sexual urges.

The process, officially called "therapeutic testicular pulpectomies ... are performed upon a written request of an adult man," the Czech government responded. It said the operation had to be approved by a committee of experts.

"Prior to the performance of such intervention, the patient must express his consent with its performance. Castration is considered with respect to men who cannot manage their sexual instincts and are sexually aggressive," the Czech government said, saying the Council of Europe had not proven its case sufficiently for the country to abandon castration.

It argues the procedure is effective in reducing repeat offenses.

But the Council of Europe questioned the statistics on repeat offenses and said even if they were correct, castration was not an appropriate way to reduce recidivism.

"The committee's delegation came across three cases in which sex offenders had committed serious sex-related crimes, including serial rape and attempted murder, after they had been surgically castrated," the human-rights group said.

"Surgical castration is no longer a generally accepted medical intervention in the treatment of sex-offenders," the report said.

It said candidates for castration often received information about the procedure which was too technical to understand -- or no information at all.

"Several patients who had undergone surgical castration told the delegation that they would never have applied for surgical castration had they been properly informed," the report warned.

It condemned the practice as "an irreversible intervention that always leads to infertility and, in the long run, a significantly increased risk of osteoporosis," also warning of possible depression and changes in appearance.

It said it was impossible to determine how many people had been castrated in keeping with a 1966 law.

The Council of Europe delegation visited the Czech Republic from March 25 to April 2, 2008. It issued its report and the Czech response on July 23, 2008. It made them public on Thursday at the request of the Czech government, it said.

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