MADRID (Reuters) - A bill to allow euthanasia and assisted suicide in certain cases cleared its first hurdle in the Spanish parliament on Tuesday, in a win for Spain's new left-wing government that will reignite a bitter debate on the issue.

In a vote on whether to allow the bill to proceed in the 350-seat parliament, 203 lawmakers voted in favor, 140 against and two abstained. The bill will be debated further before being subject to a final vote.

After two previous attempts to change the law failed due to a lack of support and the premature end of the previous legislature last year, the government was able to achieve a majority through the support of the centre-right Ciudadanos and a handful of smaller parties.

"We're talking about clearly debilitating diseases without a cure, without a solution and which cause significant suffering," government spokeswoman Maria Jesus Montero said, adding that doctors who object to the practice will be able to opt out.

Under the current law, helping someone end their life carries a jail term of up to 10 years, but 84% of Spaniards are in favor of decriminalization, according to a 2018 national opinion poll.

Euthanasia involves a physician taking an active role in ending a patient's life whereas in assisted suicide the doctor provides a lethal substance for the patient to self administer.

The Catholic Church - historically a lodestar for public opinion in Spain - considers euthanasia to be morally wrong, and the main conservative opposition People's Party (PP) and far-right Vox also want it to remain a criminal offense.

But the church's influence has been on the wane ever since Francisco Franco's dictatorship ended in 1975.

Vox spokeswoman Rocio Monasterio said her party would mount "fierce" resistance to the bill, which she said would allow people whose life was no longer considered useful to be "eliminated".

Euthanasia has attracted much attention in Spain, which has one of the world's highest life expectancies, particularly since the 2004 film "Mar Adentro" (The Sea Inside) catapulted the issue into the national spotlight.

The film tells the story of how Ramon Sampedro, a paralyzed man who for decades campaigned for the legal right to die, committed assisted suicide after courts denied him that right.

Portugal is also debating legalizing euthanasia, while euthanasia and assisted suicide are allowed in Switzerland, the Netherlands and Belgium in certain circumstances and under strict local regulations.

(Reporting by Emma Pinedo, Nathan Allen and Joan Faus in Madrid and Catarina Demony in Lisbon, editing by Andrei Khalip, Alexandra Hudson and Giles Elgood)