Assisted suicide could be offered to Britons who are chronically depressed rather than terminally ill, says the head of a controversial Swiss group.
Anne Turner is one of 54 Britons to have died at Dignitas
Ludwig Minelli says his organisation, Dignitas, is asking the Swiss Supreme court to allow a change in the law.
Existing laws have already allowed Dignitas to help 54 Britons to die and Mr Ludwig said another British man was due to follow next week.
Speaking at the Lib Dem conference, he urged the UK to drop its suicide laws.
His appeal comes after an attempt to relax the current ban on assisted dying was blocked by the House of Lords in May, although it is expected to be reintroduced.
Mr Minelli's appearance at a Lib Dem fringe meeting in Brighton was the first time he has spoken about Dignitas in the UK.
He was joined at the meeting by Sophie Pandit, whose mother, Anne Turner, died at the Zurich clinic in January.
Mr Minelli said: "The question for politicians in Britain today is why do you force your citizens, people in the most terrible circumstances who are determined to end their suffering in a way of their own choosing, to leave their country and travel to Switzerland to exercise their free will.
"Where's the humanity in this?"
Dignitas takes advantage of Switzerland's liberal laws on assisted suicide, which suggest that a person can only be prosecuted if they are acting out of self-interest.
Mr Minelli was asked whether there were any circumstances in which he would refuse to help somebody to die, especially as some argue that people with depression might make decisions they would regret if they had lived.
He replied: "I would never say no. I would say perhaps."
He said doctors in his Swiss canton would lose their licence if they prescribed lethal barbiturates to somebody who had suffered chronic depression for 10 years to commit suicide.
But Dignitas was helping a Swiss national with bipolar who lived abroad to challenge that rule in Switzerland's Supreme Court.
The organisation wants access to barbiturates without the need for a prescription.
The hearing is due to take place in October, although there will be no immediate decision.
Mr Minelli said he was not sure the man at the centre of the case would necessarily go ahead with his suicide.
But he argued: "Opening an emergency exit to these people is very important.
"These people who live in a sort of tunnel, they have just two exits which are both horrific.
"Either to go on until the so-called natural death or make a lonely suicide with all of the terrible risks."
Mr Minelli said allowing assisted suicides could reduce the number of suicides as people would get help for their problems.
And it would considerably reduce the amount of failed suicide attempts, which had severe consequences for the person involved and their friends and families.
Ms Pandit gave a heart-rending account of how she had accompanied her mother, who had progressive supranuclear palsy, to die in the Dignitas clinic earlier this year.
She said she and her siblings had been against the idea until her mother tried a "DIY home suicide" by overdosing on drugs and putting a plastic bag over her head. The attempt failed.
"Here was an intelligent woman of sound mind who wanted to die before her life became a living torture," said Ms Pandit. "We realised if we really loved our mother we should support her in her wishes."
Technically, she could have been prosecuted for helping an assisted suicide, she said. Such cases had made the law a "mockery".
The Lib Dem conference voted in 2004 to allow doctors to help terminally ill people die.
MEP Chris Davies, who organised Mr Minelli's visit, said he wanted the UK to follow the Dutch example, where there are key safeguards on assisted suicide, including ensuring the patient is mentally competent, terminally ill and suffering unendurably.
But he noted there were calls in the Netherlands for some of the safeguards to be relaxed.