The actress Julie Walters, who is also a mother, recently appeared in a dramatisation of the last days of Anne Turner, who travelled to Switzerland in 2006 with her two children to commit suicide. Walters said that the scene in which Dr Turner said goodbye to her children was so sad that she could only read it once.

On Thursday Peter and Penelope Duff became the latest Britons to make a journey to a rented Swiss flat their last. If they saw Walters' performance they were not deterred. They died together, in the company of their own children, from lethal doses of barbiturates provided by the non-profit assisted suicide group, Dignitas.

Both the Duffs had terminal cancer in its advanced stages. A spokesman for a British charity opposed to assisted suicide has called their case “desperately sad and unusual”, and so it was - at least in its details. But its basic facts are less and less unusual. Around 100 Britons have so far enlisted Dignitas to help them to end their lives. Nearly 700 more have registered with the organisation. That number is sure to grow faster than hitherto after the Lord Chief Justice's statement that there are “broad circumstances” in which helping someone to commit suicide should no longer be considered an offence.

So far Gordon Brown has ruled out changing the law for fear of loss of clarity about the value of human life. Privately he has said he is loath to provoke a public debate on the subject lest it be dominated by the most shrill and reactionary voices and produce legislation that is not progressive. Writing new laws should not, indeed, be the default response to personal tragedies. But in the absence of proper parliamentary discussion the terms of one of the most profound and urgent ethical debates facing the country are being set by a private Swiss organisation operating entirely beyond Westminster's reach.

Dignitas charges about £3,000 per person for its services, which means that it offers choice in the manner and timing of one's death, but only for those who can afford it. Unlike the House of Lords Assisted Suicide Bill sponsored by Lord Joffe but so far denied a second reading, Swiss law - and Dignitas - do not require a terminal diagnosis for assisted suicide to be legal. But its clients must be in Switzerland to die, and some of those coming from Britain end their lives earlier than they would otherwise in order to be able to travel in reasonable comfort.

The British institutional response has been piecemeal at best. The Director of Public Prosecutions set an important precedent last year by refusing to prosecute the parents of Daniel James for helping him to commit suicide in Switzerland after a rugby accident. The Lord Chief Justice's remarks last month confirmed the significance of the James case, and this week the General Medical Council's new guidelines on withholding life-prolonging treatment shifted control partly from doctors to patients.

Parliament's silence has been deafening. Both main parties are complicit; their reluctance to grapple with assisted suicide is being mocked by reality. The country needs a full debate that guards at all costs against a drift from the “right to die” towards a “duty to die”, but also ends the absurdities that drive critically ill people abroad, never to return. Lord Joffe's Bill should be the starting point.