The Italian government has been plunged into a constitutional crisis over the fate of a 38-year-old woman who has been in a coma for the past 17 years. Eluana Englaro was left in a vegetative state after a car crash in 1992. After a decade-long court battle, doctors reduced her nutrition on Friday in preparation for removing her feeding tubes, which her father claims would be in accordance with her wishes.

But in an extraordinary turn of events, the country's prime minister, Silvio Berlusconi, after consultation with the Vatican, has issued an emergency decree stating that food and water cannot be suspended for any patient depending upon them, reversing the earlier court ruling. On issuing the emergency decree, Berlusconi declared: "This is murder. I would be failing to rescue her. I'm not a Pontius Pilate."

Justifying his campaign to save Englaro's life, the prime minister added that, physically at least, she was "in the condition to have babies", a remark described by La Stampa newspaper as "shocking". Giorgio Napolitano, Italy's president, has refused to sign the decree, but if it is ratified by the Italian parliament doctors may be obliged to resume the feeding of Eluana early this week.

But, in a moving interview with the Observer, Eluana's father Beppino said last week that the doctors were carrying out his daughter's wishes by allowing her to die. "If she couldn't be what she was (before the accident in 1992) then she would not have wanted to live".

The case has deeply divided Italian society and raised concerns over the influence of the Vatican. Yesterday Pope Benedict indirectly referred to Englaro in a message delivered to mark the World Day of the Sick, stating that society had a duty to defend "the absolute and supreme dignity of every human being" even when "weak and shrouded in the mystery of suffering". But even some of Berlusconi's political allies, including the president of the lower house of parliament, Gianfranco Fini, have stated that the supreme court ruling should be obeyed and Englaro should be allowed to die.

Opposition leader Walter Veltroni, of the centre-left Democratic party, said the government should leave the Englaro family in peace and warned that Berlusconi's intervention "could cause a very dangerous constitutional crisis". Last night demonstrations in support of Eluana's right to die and the supreme court ruling were taking place across Italy.

Meanwhile, doctors are continuing to act according to the original supreme court ruling. On Friday morning in the La Quiete clinic in Udine, northern Italy, they began reducing the amount of food in Eluana Englaro's feeding tube, according to a precise medical protocol that will see nutrition gradually replaced with sedative and anti-convulsant medication. Experts say that within four to five days her condition may have deteriorated to an irreversible extent, though it might be two weeks or more before her heart stops. The process means the Englaro family and their doctors are now in a race against time as they try to end Eluana's life before the Berlusconi government and its backers in the Vatican halt the process.

Beppino, 67, was last night in the family home in Lecco, 30 miles north of Milan, caring for his wife and Eluana's mother, Saturna, who is gravely ill with cancer. After a long, agonising fight to allow his daughter to die, he described the government's last-ditch attempts as "a grotesque attack on my family".

Prior to issuing the decree, Berlusconi was involved in frantic telephone exchanges with the Vatican head of state, Cardinal Tarcisio Bertone, who implored the prime minister to prevent Eluana's death. The cardinal reportedly told Berlusconi: "We have to stop this crime against humanity."

Doctors have confirmed that, after 17 years and with such catastrophic brain damage, Eluana will never regain consciousness or awareness. The anaesthetist caring for her, Professor Antonio de Monte, said: "Eluana died 17 years ago."

Right-to-die cases

Tony Bland

During the 1989 Hillsborough disaster Bland, from Keighley, Yorkshire, suffered two punctured lungs, blocking oxygen flow to his brain and was left in a persistent vegetative state (PVS). After campaigns on both sides, the House of Lords ruled in 1993 that withdrawing treatment, as advised by a doctor and approved by Bland's parents, was lawful.

Sue Rodriguez

Diagnosed with amyotrophic lateral sclerosis in 1991, Rodriguez began a campaign against Canada's law forbidding medically assisted suicides. Her two-year legal battle ended with the Canadian supreme court ruling against her. Rodriguez eventually found a physician willing to assist in her death in 1994.

Terri Schiavo

Respiratory and cardiac arrest in 1990 caused Schiavo massive brain damage leading to PVS. After eight years, her husband Michael Schiavo petitioned the Florida courts to have her life support removed. Terri's family appealed, leading to a seven-year legal battle. Her feeding tube was finally removed in 2005.

Daniel James

The former England youth rugby player, 23, was left paralysed when a scrum collapsed. In need of 24-hour care, he applied to the Dignitas suicide clinic and travelled with his parents to Switzerland last September. James's parents were caught up in a tabloid frenzy on their return.

Craig Ewert

Ewert's assisted death caused headlines when he allowed it to be filmed for a Sky documentary, Right to Die, screened in December 2008. The former university professor, from Harrogate, North Yorkshire, was suffering from motor neurone disease and was filmed at Dignitas's clinic kissing his wife goodbye and then drinking a lethal mixture.

Richard Rogers