The parliament in Portugal has thrown into doubt a law for limited adoption rights for same-sex couples.

The first reading of the bill had been passed by lawmakers last year. But the centre-right Social Democratic Party used their majority to force a referendum on the issue by an 11 vote margin.

Their junior coalition partner in the government, The Popular Party abstained.

The result sparked protests in the public gallery while political opponents accused the Social Democrats of trying to divert attention from the country’s economic troubles.

Portugal became the eighth country to allow nationwide same-sex marriages in 2010 but the right to adopt was not included.

The proposed referendum will address the so-called co-parenting which allows members of homosexual couples to adopt children of their spouses.

Friday’s vote still has to be approved by the Constitutional Court and by the President.