The group sat down in the parliament’s public viewing gallery early on Wednesday morning without anybody realizing they belonged to the activist group.
When Justice minister Alberto Ruiz Gallardón began addressing Parliament, three of the women took their tops off and shouted “abortion is sacred”, a line they also had written on their bare bodies.
They were applauded by members of left-wing party Izquierda Unida as they removed by security.
FEMEN have been gearing up to launch a campaign to "fight patriarchy" in Spain.
Footage of the protesters in Spain's Parliament on Wednesday.
In August their members told the Spanish press they were taking part in what they described as "summer training camp" in techniques of civil disobedencience at their Paris headquarters.
Spain's conservative government said recently it would present a stricter abortion law to parliament in October.
Prime Minister Mariano Rajoy came to power in 2011 promising to change a more liberal abortion law passed the previous year by the then Socialist government.
Rajoy's conservative Popular Party and the Roman Catholic Church have hotly opposed the 2010 abortion law, which allows abortion up to 14 weeks of pregnancy or up to 22 weeks if the foetus is deformed.
Now the government seems set to return Spain to the earlier 1985 law, which decriminalized abortion only in cases of rape, deformation of the foetus or serious physical or psychological risks to the mother.