LISBON Portugal's parliament on Wednesday overturned the presidential veto on a bill legalising adoption by same-sex couples, which means conservative President Anibal Cavaco Silva will have to sign it into law before his term ends in March.

The motion was passed by 137 votes in the 230-seat parliament, bringing together the ruling Socialists, their far-left allies - the Communists and Left Bloc, and some opposition deputies from the Social Democratic Party. The rightist CDS voted against.

Parliament also overturned Cavaco Silva's veto on changes to the law on abortion. The changes eliminate co-payment by patients and other obstacles to voluntary interruption of pregnancy, which were introduced by the previous centre-right government.

Cavaco Silva last month vetoed the gay adoption bill on the grounds that parliament passed it in November without having promoted a wide-enough national debate and citing doubts that it would promote the wellbeing of children.

His refusal provoked sharp criticism from human rights groups and politicians alike, who said the president had simply opted to ignore a long-running debate on the issue as well as scientific evidence of benefits of adoption, in favour of his own conservative values.

Under the constitution, he now has eight days to sign the bills into law.

Cavaco Silva, a Social Democrat, is finishing his second term with record low popularity ratings as many Portuguese blame him for having done nothing to protect them from harsh austerity imposed under an international bailout in 2011-2014.

The country last month elected centre-right politician and former TV commentator Marcelo Rebelo de Sousa to succeed Cavaco Silva in an outcome that should help maintain political balance after a dramatic swing to the left in October's parliamentary ballot.

(Reporting by Andrei Khalip; editing by Katharine Houreld)