A referendum to establish a constitutional ban on same-sex marriage in Romania has failed - after only a fifth of voters bothered to turn out.

Romanians were being asked whether they wanted the constitution changed to specify that marriage can only be between a man and a woman.

But just 20.4% of eligible voters cast ballots - short of the 30% needed.

The result may come as a suprise, as a poll on Friday indicated support for the change was as high as 90%.

Mihai Gheorghiu, president of the pro-referendum Coalition for Family, told the BBC ahead of the vote they were trying "to protect, at a constitutional level, the definition of marriage - between one woman and one man".

But after two days of voting, it seems the No campaign's strategy - to boycott the vote in the hope the turnout fell below the 30% needed to validate the referendum - was successful.

However, in practice not much will change: Romania does not recognise gay marriage or civil unions.

Dan Barna, of the opposition Save Romania Union, the only major political party to oppose the referendum, called for the government's immediate resignation for "wasting €40m ($46m; £35m) of public money on a fantasy".

The ruling Social Democrats had strongly supported the referendum.