Thousands of anti-abortion campaigners have marched in Madrid accusing the Spanish government of betrayal over an electoral promise to restrict the rights of women to terminate their pregnancies.
Reports have suggested the conservatives have been considering shelving the controversial plans, even though they have an absolute majority.
The bill allows abortion only in cases of rape or serious health risk to the mother – not for a malformed foetus.
“We have to look for new methods to protect life. The rights of the mother and the foetus must be respected,” said one young woman demonstrator.
“We have to defend life. We are the voice of those who don’t have one,” added another.
Spain had been brought into line with most of western Europe when the last socialist government relaxed abortion rules in 2010.
The conservatives admit their planned restrictions are sensitive and complicated, saying they want to work towards consensus.