Biggs, 79, is eligible for release from July 3 but his son Michael said Justice Secretary Jack Straw had yet to give any hint as to what the decision would be.
Doctors moved Biggs from Norwich prison to a nearby hospital on Sunday after he fell and broke his hip.
Michael Biggs said his father, who is being treated in the Norfolk and Norwich Hospital in Norwich, was “in pain”. “We’ve heard nothing,” said Michael Biggs. “He’s eligible for parole from July 3 but it’s a matter for Jack Straw and we haven’t had any hint.”
Earlier this week Biggs’s legal adviser Giovanni di Stefano said he expected his client to be paroled on July 3 – possibly to the hospital.
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, before making off with £2.6 million.
He was given a 30-year sentence but escaped from Wandsworth prison in south west London in a furniture van after spending 15 months in jail.
He was on the run for more than 30 years, living in Spain, Australia and Brazil, before returning to Britain voluntarily in 2001.
Biggs is barely able to walk, is fed through a tube and is expected to be cared for following his release by Barnet Council and the local Primary Care Trust near where his son lives in north London.
His family say he hopes to be free to celebrate his 80th birthday on August 8 – 46 years to the day since the heist.