LJUBLJANA, Nov 4 (Reuters) - Slovenia will hold a referendum on Dec. 20 that could overturn a new law allowing same-sex marriages, parliament decided on Wednesday after the Constitutional Court cleared the way for the vote last month.

Parliament passed a law in March giving same-sex couples the right to marry and adopt children but the measures have not been enforced yet because a civil society group called For Children appealed to the top court, calling for a referendum.

In a similar referendum in 2012, almost 55 percent of voters in the European Union member state and ex-Yugoslav republic opposed giving more rights to same-sex couples.

A number of EU states have legally recognised same-sex marriage including Britain, France and Spain, but the practice remains contentious in others.

(Reporting by Marja Novak; Editing by Mark Heinrich)

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