The group collected the signatures in only a few weeks and handed them in nearly a month before the end of the deadline by which they had to collect a minimum of 40,000 verified signatures for a viable referendum demand.

"We are bringing more than 48,000 signatures by upstanding people," said Aleš Primc, one of the heads of Children are at stake!, a group which has built its campaign on the platform that homosexual couples should not be able to adopt.

Primc promised a tolerant campaign, saying it would be "one of the most beautiful in the world".

"This will be a campaign about a mother's and a father's love, the love of the child toward his or her mother and father and about the beautiful complementary nature and sexuality of a man and a woman."

The referendum will protect children, the family and freedom, said Primc and Metka Zevnik, the other head of the group as they arrived at the parliament building this morning.

Zevnik said the signatures were dedicated to mothers, fathers and grandparents, underlining the importance of family roots. "The flowers of parents and children blossom from the roots of grandparents. This is the goal and the beauty of our campaign."

The group has been campaigning against the possibility of allowing gay and lesbian couples to adopt children long before the relevant changes to the marriage and family relations act were passed in early March.

They started collecting the signatures straight after the act was passed and reportedly got 48,000 in less than a fortnight, when the parliament halted their effort on 26 March, saying the vote would encroach on human rights.

The group then challenged the parliament's decision to stop the referendum procedure in the Constitutional Court, which decided last week that a referendum could be held. The act has not taken effect due to the referendum procedure.

The group expects the referendum to be called for a Sunday in December. Parliament Speaker Milan Brglez said on Thursday that the vote is usually called within 30 to 45 days after the demand is lodged with the parliament.

The period can be extended by up to a year, he added. It will however not be held between Christmas and New Year's, Brglez also said.