The family of Ronnie Biggs vowed to fight on for his freedom after Britain's Justice Secretary Jack Straw condemned the Great Train Robber to a likely death behind bars.
Mr Straw rejected a parole board recommendation that the 79-year-old be released, saying Biggs was “wholly unrepentant” about his crimes.
Biggs would have been a free man “many years ago” if he had complied with the sentence given to him, Mr Straw said.
The decision was branded “perverse” by Biggs’s legal advisor, who accused Mr Straw of “cruel and unusual punishment”.
Biggs’s son Michael said the decision “beggars belief”.
Biggs is seriously unwell, having suffered a series of strokes. He cannot eat or speak, can barely walk and last weekend broke his hip when he fell out of his bed in Norwich Prison.
He is now in hospital where sources said his condition had deteriorated in the past 24 hours.
His son added that the hospital had confirmed to him that his father was in a “life-threatening” condition.
“He cannot walk, he cannot talk, he cannot read or write, he cannot drink - how can he take any reoffending courses?”
He pleaded with Mr Straw to change his mind.
He added: “I hope that Mr Straw finds it in his heart to review his recommendation not to release my father. He represents no threat to society whatsoever."
In a statement, Mr Straw said: “Mr Biggs chose to serve only one year of a 30-year sentence before he took the personal decision to commit another offence and escape from prison, avoiding capture by travelling abroad for 35 years whilst outrageously courting the media.
“I am refusing the Parole Board’s recommendation for parole. Biggs chose not to obey the law and respect the punishments given to him – the legal system in this country deserves more respect than this."
Biggs was eligible for release on Friday, having served 10 years of his 30-year sentence.
The Parole Board, which met earlier this month, recommended his release saying he posed a “manageable” threat to the public.
But it noted he was unrepentant about fleeing prison and going on the run for 35 years.
Biggs, from Lambeth, south London, was a member of a 15-strong gang which attacked the Glasgow to London mail train at Ledburn, Buckinghamshire, in August 1963, and made off with £2.6m in used banknotes.
He was given the 30-year sentence but after 15 months he escaped from Wandsworth prison in south-west London by climbing a 30ft wall and fleeing in a furniture van.
He was on the run for more than 30 years, living in Spain, Australia and Brazil, before returning to the UK voluntarily in 2001 in search of medical treatment.
He was locked up in Belmarsh high security prison on his return before being moved to a specialist medical unit at Norwich prison.
The decision means Biggs will not be free to celebrate his 80th birthday on August 8, 46 years to the day since the raid.