The result - a 1% majority for retaining the existing restrictions - would have been binding only if more than half the electorate had voted.

A BBC correspondent in Lisbon says the Socialist party has decided against continuing with the bill because it would have been politically risky to do so.

President Jorge Sampaio was known to favour the proposal but kept his opinions to himself. The prime minister, Antonio Guterres, is a practising Catholic and opposed the proposal, though most of his party supported it.

Their appeals to citizens to exercise their vote clearly fell on deaf ears. Politicians had feared a turnout of less than 50% would undermine faith in the political system.

Clear stand by church

In this overwhelmingly Catholic country, where the church has taken a clear stand against abortion, many voters who might have voted in favour have been reluctant to express a firm view.

Parliament approved a bill relaxing abortion restrictions in February, but opponents successfully pushed for a national ballot on whether to overturn or ratify the legislation.

At present, abortions are allowed only for strict medical reasons or in cases of rape, and women can be jailed for up to three years for having an illegal abortion.

The law elsewhere in Europe: