BRATISLAVA (Reuters) - Slovakia will not ratify a European treaty designed to combat violence against women, Prime Minister Robert Fico said on Wednesday bowing to opposition from junior coalition partner and religious groups.

Two weeks ago, Bulgaria, which now holds the EU’s rotating presidency, has also rejected the treaty, highlighting resistance in the more socially conservative countries of the former eastern bloc to the liberal values of wealthier western Europe.

Slovakia’s government signed the 81-article document in 2011 and parliamentary ratification would have been the next step. In all, more than 40 countries have signed.

But Fico said that though Slovakia would adopt into law all measures aimed at combating violence against women, it would not ratify the treaty, which he said was a controversial document that could violate the constitution and lead to the introduction of same-sex marriage.

Slovakia effectively banned gay marriage when it passed a constitutional amendment in 2014 that defines marriage as a union between a man and a woman. It does not recognise any form of same-sex civil partnership either.

“We can not pass measures that would clash with beliefs and feelings of people in some states,” Fico, a Social Democrat, said.

The European convention “needlessly questions natural differences between men and women and calls them stereotypes” while pursuing the fine goal of eliminating violence against women, he said.

A junior coalition Slovak National Party (SNS) said on Thursday it would go as far as demand that Slovakia withdraws its signature from the document.

The critics dispute the treaty’s definition of ‘gender’ as “social roles, behaviours, activities and characteristics that a particular society considers appropriate for women and men”.

The Roman Catholic Church said the document may lead to discrimination of religious freedom in the country of 5.4 million people, where 62 percent identify as Roman Catholics and 6 percent as Protestants, according to a 2011 census, the latest available.

EU members Bulgaria, Hungary, the Czech Republic, Britain, Croatia, Greece and Ireland have not signed treaty yet and neither have Council of Europe members Azerbaijan and Russia.