The Vermont legislature passed a bill allowing physicians to approve lethal drugs for terminally ill patients to kill themselves, a move the local Catholic diocese said will have major consequences.

"Physician-assisted suicide will forever transform the role of physician from one who preserves life to one who takes life," the Catholic Diocese of Burlington said ahead of the vote on its website.

"Catholics must raise their voices against such an affront to human life," the diocese added. "True compassion calls us to embrace those who are dying, not provide them with the means to end their lives."

On May 13, the Vermont House approved the bill by a vote of 75 to 65. Last week, the Senate passed the bill by a vote of 16-14. Gov. Peter Shumlin, a Democrat, has said he will sign the bill.

The bill allows the prescription of lethal drugs to patients suffering from an "incurable and irreversible disease" and who have a life expectancy of six months or less, Reuters reports. The patient's primary physician and a consulting doctor must agree that the patient's diagnosis is terminal and that the patient is capable of informed consent.

The patient must request the drugs twice, with a 15-day period between the requests. The patient must self-administer the drugs.

Gov. Shumlin said the bill will offer the state's citizens who have terminal illnesses "a choice to control their destiny and avoid unnecessary suffering."

Opponents of the bill have said it could encourage people to kill themselves out of fear they are imposing a burden on their family or out of undue influence from potential heirs.

Bishop Salvatore R. Matano of Burlington spoke out against "doctor-prescribed suicide" in a letter reissued January 22.

"As we care for the child so must we care for all persons in the vast spectrum of life," the bishop said. "When we subjectively determine when life begins and ends, when it is viable or not, when it is too burdensome to endure, we begin a path toward self-destruction. Life is no longer precious, but just another commodity in the business of living."

He warned that the legislation would allow health insurers and government agencies to encourage the seriously ill to take lethal prescriptions rather than seek life-extending treatment. He said at least two such cases have become public in states where the form of suicide is legal.

Bishop Matano urged that society provide support for the terminally ill. Willfully killing those who are sick, disabled or dying is "morally unacceptable and a tragic offense against life," he said.

Doctor-assisted suicide is legal in Oregon and Washington state after voters approved ballot initiatives in favor of legalization. Since the Oregon law took effect in 1997, 673 people have killed themselves with drugs prescribed under the law, the Oregon health department reported earlier this year.

In 2012 Massachusetts voters narrowly defeated a ballot measure to legalize doctor-assisted suicide by a margin of 51-49.