Making assisted dying legal would mean "less suffering not more deaths", a leading campaigner has said as peers debated the issue in the House of Lords.
Lord Falconer, who proposed the bill, said a "limited" change was needed to the law to give the terminally ill choice on their deaths.
He insisted that the "final decision must always be made by the patient", with safeguards to prevent "abuse".
Lord Falconer's private member's bill would allow doctors to prescribe a lethal dose to terminally ill patients judged to have less than six months to live.
The bill is expected to get a second reading in the Lords, but without government backing MPs are unlikely to get a chance to debate it in the Commons.
This means that it will not become law.
Prime Minister David Cameron has said he is not "convinced" by the arguments for legalising assisted dying but the bill has won the backing of Lib Dem Care Minister Norman Lamb.
The DUP's Lord Morrow has voted against the Bill.
He claimed the legislation proposed by Lord Falconer was "ill-conceived" and asserted that most terminally ill people wanted to spend time with their families while being properly cared for.
He said: "The role of any legislature is to protect the most vulnerable in society and to give them a voice. The majority of charities and advocacy groups for the terminally ill oppose assisted suicide and a change in the legislation, precisely because terminally ill people often do not want their life ended, rather they wanted to be cared for and spend time with their families."
He said provision of proper care for the dying was the key.
"The most loving and caring thing that we as a society can do for our terminally ill, is not to end their life, but rather to provide them with the best possible care and help them live out their life in dignity and with respect."
Former Conservative Party Minister Norman Tebbit, whose wife was permanently disabled in the IRA bombing of the Tory Party conference in Brighton, and who has cared for her since, also opposed the bill.
He said it created the financial incentive for "vultures" to swarm over the sick and dying.
He said: "I am concerned at the financial incentives to end the lives of the frail, the handicapped, the ill and the elderly.
"Those who care for such people are all too familiar with the moments of black despair which prompt those words: 'I would be better dead so that you could get on with your life'."