The bill, which is currently under consideration at the Federation Council Social Policy Committee, would allow patients suffering from incurable diseases to be euthanized at their own request.
But Nikolai Gerasimenko (United Russia), deputy chairman of the State Duma Health Committee, said euthanasia could not be applied in Russia, adding that it could "become a weapon in the hands of unscrupulous doctors and lawyers."
He said Russia still has no law guaranteeing provision of good quality medical services for all individuals or a law on healthcare.
Another pro-Kremlin MP said the bill effectively legalizes suicide and murder.
"We are being told that the quality of medical care in Russia is very poor, but this only highlights the need to improve the quality, not attempt to eliminate the problem by sanctioning suicide," said Duma Deputy Speaker Vladimir Katrenko (United Russia).
He also said many of the "hopeless patients" are known to have recovered later.
Vladimir Zhirinovsky, leader of the ultra-nationalist Liberal Democratic Party and deputy speaker of the State Duma, said it would be premature to legalize euthanasia in Russia because demand would be too high.
"This is dangerous. There would not be enough morgues so the entire state budget would have to be spent building new ones," he said, adding many people would accept euthanasia as a way out of difficult living conditions, while others would be forced by their relatives in an effort to "inherit" their apartments.
"In 20 years, euthanasia will be okay here, but now it is too soon," he said.
Opposition to the bill also came from organizations providing palliative care for the terminally ill.
Vera Millionshchikova, chief of Moscow's first hospice, said it was wrong to deprive a person of his life, even if seriously ill, adding no effort must be spared to help a terminally ill patient and that life must be treated as a divine gift.
The opposition was joined by the Russian Orthodox Church.
"From the ROC perspective, both suicide and assisted suicide are totally immoral," said Vsevolod Chaplin, deputy head of the Moscow Patriarchy's department for external relations.
He cautioned against reckless, rash decisions on the matter.
"If such a bill really exists, it must not be passed in haste, merely on the basis of expert opinion (doctors, lawyers, etc.), especially lobby groups," he said.