The change would have allowed loved ones to accompany the dying abroad
A move to make it legal to help a terminally ill person to die has been defeated in the House of Lords.
The measure would have removed the threat of prosecution from those who go abroad to help an "assisted suicide".
It was proposed by former Labour Lord Chancellor Lord Falconer who said there was a legal "no-man's land" that required clarity.
At least 115 people from the UK have gone to Swiss clinic Dignitas to die, but as yet no-one has been prosecuted.
In a free vote the Lords defeated the amendment to the Coroners and Justice Bill by 194 to 141.
The debate in the Lords thrust the issue of assisted suicide back into the spotlight and drew sharp criticism from church leaders and advocates for the disabled.
Lord Falconer said helping someone go abroad to die should be allowed under a set of strict rules.
Such actions were deemed illegal under the Suicide Act.
The amendment called for the law to be waived if two doctors confirmed the person in question is terminally ill and deemed competent enough to make such a decision to end their life.
The motion also called for the person who wanted to die to declare that it is their decision to have an assisted death abroad and this should be witnessed by an independent person.
Lord Falconer said that while several cases of assisted suicide abroad had been the subject of police investigations, no-one had faced a criminal prosecution.
"Nobody wishes to prosecute in those cases because nobody, in my view correctly, has the stomach to prosecute in cases of compassionate assistance."
He was supported in his move by Dignity in Dying.
However, the Bishop of Exeter, the Rt Rev Michael Langrish, who has a 30-year-old daughter with Down's syndrome, told the Lords that the amendment would be "a legislative milestone on that slippery slope to introducing assisted suicide here in the UK by incremental degrees".
The move to change the law came after Debbie Purdy, a 46-year-old from Bradford who is terminally ill with multiple sclerosis, fought a series of court battles over the issue.
She has asked for clarification over whether her husband would face prosecution for helping her travel to Switzerland.
She has already lost High Court and Appeal Court cases and then took her case to the Law Lords.
The Care Not Killing Alliance, an umbrella group of doctors and organisations opposed to changing the law, labelled the amendment "dangerous".
They argued it runs the risk of vulnerable people being pushed into going to clinics like Dignitas against their will.