Under Poland's centre-right government law, chemical therapy is mandatory for paedophiles convicted of raping children under the age of 15 years or a close relative.
"The purpose of this action is to improve the mental health of the convict, to lower his libido and thereby to reduce the risk of another crime being committed by the same person," said the government.
Prime Minister Donald Tusk said in 2008, he demanded obligatory castration for paedophiles, whom he termed as 'degenerates'.
Tusk said he did not believe "one can use the term 'human' for such individuals, such creatures".
"Therefore I don't think protection of human rights should refer to these kind of events," he said.
However, the human rights groups objected to the law.
"Introducing any mandatory treatment raises doubts as such a requirement is never reasonable and life can always produce cases that lawmakers could never have even dreamt of," said Piotr Kladoczny from the Helsinki Foundation of Human Rights.
"If somebody is of sound mind, we punish him. If he is sick, we try to cure him - that's how it works in Polish law.
"This bill introduces both approaches. As far as I know, this makes our law the strictest in Europe on this issue."