Speaking in support of women seeking abortion, Pilar Bardem, an actress, called for "respect" for women who had made the "very difficult" decision to terminate a pregnancy.

Spain decriminalised abortion in 1985 but only for certain cases - up to 12 weeks of pregnancy after a rape; up to 22 weeks in the case of malformation of the foetus; and at any point if the pregnancy represents a threat to the physical or mental health of the woman.

But Spain's Socialist government last month said it plans to introduce a law that will offer greater legal protection for women who wish to have an abortion and doctors who carry out the procedure.

The Women on Waves ship visited Ireland in 2001, Poland in 2003 and Portugal in 2004, sparking protests in each country.