The driving forces behind the change were the country's ruling former Communists and a variety of women's groups who argued that the law, passed in 1993, had forced tens of thousands of Polish women to turn to back- street abortions.
Under the new law, women will be able to have abortions up to the 12th week of pregnancy. Church leaders described the vote as a "tragic decision".
The abortion debate has raged in Poland ever since the overthrow of Communism in 1989, serving as a useful barometer of the Church's influence over Polish society.
As almost everywhere else in the former Eastern bloc, abortion was available on demand in Poland for most of the Communist era, but, afterintense pressure from the Church, tough anti-abortion legislation was passed in 1993 by a centre-right coalition containing pro-Catholic, pro-Life parties. Under the terms of the current law, abortions in Poland are permitted only if the pregnancy results from rape or incest, if the life or health of the mother is judged to be at risk or if the foetus is irreparably damaged. Doctors caught transgressing the regulations are liable to two years' jail.
In addition to sparking a surge in back-street abortions, the 1993 law spawned "gynaecological tours" to neighbouring countries such as Belarus and Ukraine, where pregnancies can be terminated with no questions asked. It also led to an increase in the number of babies being abandoned.
Condemning what many of its members saw as a return tomedieval clericalism, the SLD signalled its intention to reintroduce a liberal abortion law after its 1993 election success - although its passage was repeatedly vetoed by former President Lech Walesa, a devout Catholic and a father- of-eight.
On the other hand, Mr Walesa's successor, Aleksander Kwasniewski, himself a former Communist, has already made clear his support for the liberalised law, which should now come into force later this year.
But, within minutes of yesterday's vote, right-of-centre parties, now grouping around the Solidarity trade union, said they would seek to reverse the changes should they win next year's parliamentary elections.Reuse content