A wafer-thin majority of those who voted rejected the proposal that women should be granted the right to abort on demand in the first 10 weeks of pregnancy, a deeply divisive issue in the overwhelmingly Catholic country.
With only a couple of the country's more than 4,200 districts left to count, the "No" vote had some 51 per cent support against 49 per cent for the "Yes".
But as only some 30 per cent of the country's 8.5 million electorate took part, voters in effect dumped the controversial issue back in the lap of parliament where moves were already underway to make abortion easier.
A turnout of more than 50 per cent was needed for the result of Portugal's first ever referendum to be binding on the legislature.
Under existing Portuguese law, termination of pregnancy is permitted only for strictly defined medical reasons or in cases of rape, and only until the 12th week. People will decide whether abortion on demand through the 10th week of pregnancy should be "decriminalised," which in effect will eliminate current prohibitions.
Parliament in February approved a bill relaxing abortion restrictions, but the bill's opponents successfully pushed for the national ballot which will either overturn or ratify that legislation.
An intense two-week campaign leading up to the ballot featured marches in big cities and a nationwide media blitz.
Abortion rights activists, mostly the younger generation backed by left- wing politicians, say they want to end the estimated 16,000 illegal abortions each year in Portugal, a nation of 9.5 million people.
Government statistics indicate that each year about 10,000 women are treated at hospitals following botched illegal abortions. Women can be imprisoned for up to three years for having an illegal abortion.Reuse content