MPs backed the government's Mental Capacity Bill last night after Tony Blair stepped in to allay claims that the legislation will not allow euthanasia by the back door.

The prime minister held telephone conversations with the Archbishop of Westminster, Cardinal Cormac Murphy-O'Connor, while constitutional affairs secretary Lord Falconer held talks with Peter Smith, the Catholic Archbishop of Cardiff.

The government then put forward two concessions. It said that "living wills" will be written and witnessed and secondly that doctors or the patient's agents should not be motivated to bring about the patient's death.

This reduced the Labour rebellion down to 34 MPs with a further 100 abstentions.