Liberal Democrat leader Vince Cable has declared his support for a change in the law to allow assisted dying.
Mr Cable, once a firm opponent, admitted he had changed his mind on the difficult ethical issue.
Writing in the Daily Mail, he said he believes his fears about how such a system could be abused have been allayed by arguments for strict safeguards as part of any law change.
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Mr Cable said he had held concerns "about 'slippery slopes' and how a system of assisted dying could be abused by greedy relatives bringing pressure to bear and overworked doctors (or worse) signing on the dotted line if asked; and how the elderly and disabled would fear coming under pressure to stop 'being a burden'."
But, he added: "Having talked at length to some of the campaigners for assisted dying it is clear that these fears and reservations can be addressed: that strict safeguards can be built in to protect both the patient and the doctors involved."
'Change in law'
He said a law change is a matter for Parliament and that the Government should "take the lead".
He added: "But, failing that, I am one of a growing number of MPs willing to support private members' legislation in Parliament."
Mr Cable said he had discussed the matter with his wife Rachel and said they both agreed that "if 'assisted dying' were legal, we could not allow the other to suffer intolerable pain should they wish to bring it to an end".
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It comes days after Geoff Whaley, 80, of Chalfont St Peter in Buckinghamshire, arranged to end his life at a Dignitas clinic in Switzerland to avoid a protracted death from motor neurone disease, which he was diagnosed with two years ago.
His wife Ann, 76, supported his decision but reportedly said his final weeks were marred by police inquiries over her involvement in his plans.
Officers dropped the case but the couple called for the law to be changed to allow assisted dying in some circumstances.
In UK law, helping someone to end their life is punishable by up to 14 years in prison.