Gordon Brown today made plain that he would block any move to relax the law on assisted suicide, less than a month after he first revealed that he opposed new legislation.

In a radio interview, the Prime Minister said that he was not prepared to consider any measures that might put vulnerable people under pressure to agree to end their own lives. The law should make “absolutely clear” that it recognised the value of human life, he said.

Cardinal Cormac Murphy-O’Connor, the Roman Catholic Archbishop of Westminster — acting as guest editor of the Today programme on Radio 4 — had asked the Prime Minister whether he would support laws to permit euthanasia or assisted suicide.

Mr Brown responded: “I am totally against laws on that . . . It is not really for us to create any legislation that would put pressure on people to feel they had to offer themselves because they were causing trouble to a relative or anyone else.

“I think we have got to make it absolutely clear that the importance of human life is recognised.”

Debate on the emotive subject was stoked at the start of this month, when a television documentary showed footage of an assisted dying that included the moment of death. Craig Ewert, 59, a motor neuron disease sufferer from Harrogate, North Yorkshire, was shown on the Sky TV Real Lives channel, dying from a dose of barbiturates. He had travelled to the Dignitas clinic accompanied by Mary, his wife of 37 years.

The documentary prompted renewed calls from campaigners for a change in the law in the wake of several cases of British people travelling to Switzerland to die.

At present, British law makes it a criminal offence to “aid, abet, counsel or procure” someone else’s suicide, although doubts were raised over how strongly the law might in future be enforced after the Director of Public Prosecutions decided this month not to charge the parents of Daniel James, 23, who accompanied their tetraplegic son to the Dignitas clinic in Zurich to allow him to die.

After the documentary was shown, Mr Brown surprised MPs by revealing that he had strong views on the subject. "I believe that it's necessary to ensure that there is a never a case in the country where a sick or elderly person feels under pressure to agree to an assisted death or somehow feels it's the expected thing to do. That's why I've always opposed legislation for assisted deaths," he said.

Campaigners for assisted dying criticised Mr Brown's stance for denying choice to terminally ill people. James Harris, head of campaigns and communications at Dignity in Dying, which campaigns for assisted dying for terminally ill patients, said: “It should not be for Gordon Brown or Cardinal Cormac Murphy O’Connor to decide when a dying adult’s suffering should end. Within safeguards, it should be a decision for the dying adult themselves.

“The Prime Minister is out of step with public opinion. Not only is there no evidence of abuse in countries that have legalised assisted dying for the terminally ill, research shows that people are, in fact, better protected by a more compassionate and regulated approach to end-of-life decision making.

“Maintaining the status quo will lead to more people travelling aboard to die, ’mercy killings’ and botched and violent suicide attempts. Dignity in Dying believes that this is unacceptable.”

In today's radio interview, Mr Brown also told the Cardinal that the current economic crisis had made clear the need for a moral dimension to capitalism.

“This is the lesson that I think has come home through this crisis over the last year,” said the Prime Minister. “Yes, we believe in free markets, but we don’t believe in value-free markets.

“It is quite an important point that successful economies and societies are built on recognising that there are strong values that are absolutely crucial to their success — the value of hard work, taking responsibility, being enterprising but not taking irresponsible risks at the expense of other people.”

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