Biggs spent 36 years as a fugitive
Train robber Ronnie Biggs is planning to go on hunger strike in jail, his son has said.
Biggs, 76, is protesting because the Home Office has yet to decide on an application to free him on compassionate grounds.
His son Mike, 31, accused Home Secretary Charles Clarke of "prevarication of the worst kind".
He said his father was determined to refuse food from now on in protest at delays to the decision.
Biggs was sentenced to 30 years for his part in the robbery of a Glasgow to London mail train on August 8, 1963, when a 15-strong gang made off with £2.6m in used bank notes.
He escaped from Wandsworth prison in a furniture van after just 15 months in jail
Biggs returned to Britain voluntarily after over three decades on the run in Spain, Australia, and then Brazil, and was imprisoned in Belmarsh high security jail in south-east London.
Since then he has suffered a series of health scares, including minor strokes and heart attacks and contracting the hospital superbug MRSA, and has been in and out of hospital.
His solicitors say he could "die at any moment" but a previous application for release on compassionate grounds was refused because prison bosses deemed that he was not ill enough.
Mike Biggs said: "My father has had enough. He is going on hunger strike. I cannot talk him out of it.
"We appealed for my father's release on compassionate grounds.
"All the reports that were requested by the government - medical, social, nursing, independent nursing - have been sent in, we have now waited three months for a decision either way and there is still no sign of one."
He added: "There is no excuse for this delay. It's a disgrace and it's inhumane."