Amnesty International say the decision "pushes Hungary back towards the dark ages".
Hungary has approved legislation banning the legal recognition of transgender and intersex citizens.
The new law defines gender based on chromosomes at birth, changing the characteristic wording from 'sex' to 'sex assigned at birth'.
The amendment means trans people can no longer alter their gender and name on official documents, such as identity documents and marriage certificates.
"Given that the complete change of the biological sex is not possible, it is necessary to state in law that there is no possibility to change it in the registry of births, marriages, and deaths, either,'' an explanation accompanying the amendment said.
The law was originally proposed by Hungary's deputy prime minister on 31 March as part of a package of legislation amendments.
The bill was passed by 134 to 56, behind the two-thirds majority of prime minister Viktor Orbán’s Fidesz party, despite opposition from other parties.
But the legislation has been widely criticised internationally by human rights organisations, the Council of Europe Commissioner for Human Rights, and Members of the European Parliament.
“This decision pushes Hungary back towards the dark ages and tramples the rights of transgender and intersex people," said Amnesty International’s Researcher, Krisztina Tamás-Sáróy, in a statement.
"It will not only expose them to further discrimination but will also deepen an already intolerant and hostile environment faced by the LGBTI community."
“Everyone’s gender identity should be legally recognised and everyone must be allowed to change their legal name and gender markers on all official documents.”
"A nightmare for absolutely no reason"
Amnesty International had joined several international and national LGBTI organisations in calling for this ban to be dropped under the hashtag #drop33.
The campaign had received support from MEPs from parties such as Fine Gael, the Social Democratic Party of Germany and the Five Star Movement.
President of Amnesty International France, Cecile Coudriou said the organisation was "absolutely appalled but not surprised" by the Hungarian Parliament's decision.
"Hungary has been drifting away from human rights and European values for quite some time now," Coudriou told Euronews.
"Transgender people do not have the choice to be who they are ... on a daily basis, this will be a nightmare for these people for absolutely no reason."
"We will continue to ask all member states of the European Union to pressure on Hungary's government because they obviously do not respect international law.
Amnesty International is also urging for Hungary’s Commissioner for Fundamental Rights to act on the decision by Parliament and say "the fight is not over yet".
"We still have hope and we are going to continue to fight against a law which is a synonym of discrimination in a country where the climate is already hostile against LGBT people," Cecile Coudriou told Euronews.
Calls for constitutional review
The Háttér Society, a Hungarian trans rights group, added on Tuesday that the law violated international human rights norms and went against the case-law of the European Court of Human Rights.
The society has asked Hungary's president to refrain from signing the bill into law and have requested the provisions are reviewed in Hungary's Constitutional Court.
Katrin Hugendubel, Advocacy Director for ILGA-Europe has stated that "legal gender recognition is the bedrock of access to equality and non-discrimination for trans and intersex people."
"Without it, these populations are subject to immense stigma, discrimination, harassment, and violence every time they use their identity documents – be it at the bank, when going to the doctor, when applying for a job, or even when applying for a cell phone contract.”
Dunja Mijatovic, the Council of Europe's Commissioner for Human Rights, has further asked Hungary's Parliament to reject the amendments.
Meanwhile in the European Parliament, German MEP Terry Reintke, said on Twitter that the amendment was an "open attack on the rights of trans and intersex people".
Polish MEP Sylwia Spurek also described the new law as "draconian".
Viktor Orbán’s government in Hungary has previously been accused of anti-LGBT rhetoric in its policies.
In 2019, an advertising campaign by Coca Cola featuring same-sex couples was threatened with boycotts.
LGBT activists in Hungary have told Euronews that the country has seen progress, but have expressed concerns about the government’s unwillingness to enact more change.
Last month, Viktor Orbán passed a bill during the coronavirus pandemic to allow him to rule indefinitely by decree.
In an interview with Euronews, Hungary's Foreign Minister dismissed criticism of the new powers as "simply fake" and "not true".
Watch Matthew Holroyd's report in #TheCube above.