As well as saying there is no heaven or afterlife, the renowned scientist said that our brains switch off like ‘broken down computers’ when we die.
His comments upset some religious groups, already angry at his statement last year that the universe was not created by God.
Professor Hawking’s latest remarks came in an interview in which the theoretical physicist told how he had learnt to live in the shadow of death since being diagnosed with motor neurone disease aged 21.
The disease, which is incurable, was expected to kill him within a few years. Instead, he said, it ultimately led him to enjoy life more.
The 69-year-old Cambridge University academic said: ‘I have lived with the prospect of an early death for the last 49 years.
‘I’m not afraid of death, but I’m in no hurry to die. I have so much I want to do first.
‘I regard the brain as a computer which will stop working when its components fail.
‘There is no heaven or afterlife for broken down computers; that is a fairy story for people afraid of the dark.’
His remarks are more radical than those laid out in his 2010 book, The Grand Design, where he asserts that the universe is governed by the laws of science and did not need a ‘creator’ to bring it into being.
'I regard the brain as a computer which will stop working when its components fail'
In the interview Professor Hawking – who will today give a lecture entitled ‘Why are we here?’ at the Google Zeitgeist meeting in London – was asked: ‘Is our existence all down to luck?’
He replied: ‘Science predicts that many different kinds of universe will be spontaneously created out of nothing. It is a matter of chance which we are in.’
In answer to another question, he said people should use their time on Earth to fulfil their potential, saying: ‘We should seek the greatest value of our action.’
His lecture today will focus on M-theory, a broad mathematical framework in which 11 dimensions of the universe are identified and which many physicists say is the best hope yet of developing a ‘theory of everything’.
Row: Atheist biologist Richard Dawkins is another famous atheist; but Stephen Green, Christian Voice director, said Professor Hawking has a 'dim viewpoint'
Last night Professor Hawking, whose 1988 science book A Brief History Of Time has sold nine million copies, was criticised by Stephen Green, director of lobby group Christian Voice.
‘The comparisons to a computer switching off shows a man who is only able to think of things in a materialistic way,’ he said.
‘It is a dim viewpoint of a man who is trying to understand something he is spiritually unable to do.
‘People who believe in the afterlife don’t do so because they are afraid of death, that’s a misunderstanding of religious thinking.
‘Belief in God dispels a fear of the dark, of death. I don’t see why Hawking finds it such a struggle to comprehend the spiritual dimension.
‘Hawking is happy to discuss the M-theory, in which the universe is said to have 11 dimensions. Why then could the universe not have a 12th spiritual dimension?’
Earlier this month Professor Hawking explained how motor neurone disease had ultimately allowed him to be much happier.
He said: ‘I don’t have much positive to say about motor neurone disease.
‘But it taught me not to pity myself because others were worse off, and to get on with what I could still do.
‘I’m happier now than before I developed the condition.’