A controversial law which bans the promotion of gay marriage in Lithuania comes into power on Monday.

The law was amended in December after international criticism. Before, it prohibited the “public dissemination” of any materials which could be seen to promote homosexuality.

Instead, lawmakers approved changes which would ban the “encouraging the sexual abuse of minors, sexual relations between minors and other sexual relations”.

“Other sexual relations” means that campaigning for gay marriage or civil partnerships will be illegal, human rights group Amnesty International has argued.

Gay Pride marches may also be banned.

The law now classifies any information which “denigrates family values” or which “encourages a concept of marriage and family other than stipulated in the Constitution” as detrimental to children and bans it from places accessible to them.

Lithuanian law defines marriage as the union of a man and a woman.

John Dalhuisen, Amnesty International’s expert on discrimination, said: “This law will violate the freedom of expression and will directly discriminate against people on account of their sexual orientation or gender identity.

“It will stigmatise gay and lesbian people and exposes advocates for their rights to the risk of censorship and financial penalties.”

He added that the law was an “anachronism” in the European Union and called on Lithuanian authorities to scrap it.

The legislation also prohibits the mention of bisexuality, polygamy, images of straight sex, death and severe injury, the paranormal, foul language and bad eating habits.

It does not specify punishments for breaking the law.