British opponents of assisted suicide are right to warn that it will only open the door to the deaths of healthy, vulnerable people, says a Dutch pro-euthanasia campaigner.

The Dutch Medical Association Journal quotes Dr Bert Keizer as saying that the legalisation of assisted dying is the start of a "slippery slope" towards the "random killing of the defenceless." 

Euthanasia has been legal in the Netherlands since 2002 for individuals who are deemed to have "hopeless and unbearable" suffering. Initially, this applied to those with terminal illnesses but over the years, the law has been broadly interpreted to include people with non-physical issues, like psychiatric conditions and dementia.

Dr Keizer noted the law is now being widened to allow physically and mentally healthy old people to choose assisted dying if they "find that their life no longer has content". 

In July, a bill was submitted by to the Dutch Parliament proposing to allow "completed life" euthanasia.

Dr Keizer predicts that the law will be broadened further to allow euthanasia for disabled children and prisoners serving life sentences "who desperately long for death". 

"What our British colleagues had predicted years earlier, with unconcealed complacency, happened: those who embark on euthanasia venture down a slippery slope along which you irrevocably slide down to the random killing of defenceless sick people," Dr Keizer said.

"Every time a line was drawn, it was also pushed back."

Westminster has so far resisted pressure to legalise assisted suicide but Tory MP Andrew Mitchell last month predicted that the law in the UK will change within the next four years. 

He said he was not looking for "massive change" but rather "very, very tight reform". 

The Care Not Killing (CNK) alliance has said that the experience of the Netherlands "shows why assisted suicide and euthanasia should never be legalised in the UK". 

"The slippery slope is real and the Dutch euthanasia law has already been massively extended," said CNK Chief Executive Dr Gordon Macdonald.