About 63.4 percent of voters rejected the law in a referendum while 36.6 percent supported it, a preliminary result of the State Electoral Commission showed after 99 percent of votes were counted.

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

In another 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. "I personally am disappointed but I still believe that Slovenia is generally moving towards a more inclusive society and I am sure that a similar law will be enforced at some point in the future," Roman Kuhar, a male sociologist who has been living with his male partner for 11 years, told Reuters.

"The problem is that only people who are strongly against the law or strongly in its favour vote in a referendum. If most other people would cast a vote, as well, I believe the law would be enforced," he added. Turnout on Sunday was 36.2 percent.

The government supported the new law but did not participate in the referendum campaign. The main opposition party, the Slovenian Democratic Party (SDS), was against the law.

"We are against the law that would deny the basic right of a child to have a mother and a father," For Children said on its website.

The small Alpine state of 2 million citizens is relatively tolerant of gay couples who have been able to formally register their relationship since 2006 and are also allowed to adopt children from a partner's previous relationship - though not other children.

A number of EU states have legally recognised same-sex marriages, including Britain, France and Spain, but the issue remains contentious in many other EU states.

Reuters