Ian Acheson was speaking after The Metropolitan Police's counter-terrorism commander has said it is "testament to the ingenuity" of former soldier Daniel Khalife that there have been no confirmed sightings since he escaped from the London prison.
Khalife, who according to reports is accused of gathering information for Iran, went missing in his cook's uniform from HMP Wandsworth on Wednesday, prompting extra security checks at major transport hubs.
Strapping was found on the underside of a Bidfood delivery vehicle which police stopped just over an hour after it left the prison, with officers suggesting the 21-year-old held on to the underside of the lorry to escape.
The Met's counter-terrorism commander, Dominic Murphy, told reporters it was "unusual" that there had been no confirmed sightings, before praising the UK for having "some of the best military in the world".
But Ian Acheson, who previously ran security at the prison, was scathing in his assessment of security there now.
"This is a catastrophic system failure that actually starts with the allocation of Khalif to Wandsworth and ends with a terrorist suspect working in a prison kitchen of an establishment in crisis [and then] escaping in a vehicle," he told the BBC.
"So it's incredibly embarrassing for the prison service, but it's not entirely surprising, given what we know about what's going on at Wandsworth at the moment. But, you know, in order for this to have happened in one of our most iconic prisons, there would have had to have been multiple breaches of human and physical security. Wandsworth, like so many of our flagship prisons, is in freefall."
He said recent inspection reports show that from 30-44% of frontline staff are unavailable to work and that morale is very low.
"I mean, frankly, if you cannot even manage to get the bins emptied in a place like Wandsworth, what else is going wrong?"
The Met's counter-terrorism commander, Dominic Murphy, said the force had received more than 50 calls from the public which had provided "some really valuable lines of inquiry".
Mr Murphy also said he was keeping an "open mind" as to whether Khalife had received support from somebody to escape prison and whether or not he had managed to leave the country.
He said the lorry Khalife is believed to be strapped to the bottom of left HMP Wandsworth at 7.32am on Wednesday. He was declared missing at 7.50am.
Police were then notified at 8.15am and the lorry was stopped on Upper Richmond Road near to the junction of Carlton Drive at 8.37am.
In a press briefing on Thursday, Mr Murphy said: "This was a really busy area of London and we've had no confirmed sightings in any of that information, which is a little unusual, and perhaps testament to Daniel Khalife's ingenuity in his escape and some of his movements after his escape.
"It's important that we remember that we have some of the best military in the world here in the UK and he was trained.
"He was a trained soldier - so ultimately he has skills that perhaps some sections of the public don't have."
Mr Murphy added: "He's a very resourceful individual, clearly, and our experience of him shows that, so nothing is off the table with him at the moment."
The Justice Secretary confirmed an independent investigation will take place following Khalife's escape.
Alex Chalk told MPs that two urgent reviews would also take place regarding the categorisation and placement of all HMP Wandsworth prisoners and all those in custody charged with terrorism offences.
Mr Murphy said there were more than 150 investigators and police staff from counter terrorism command working in London on the "fast-paced investigation".
Chief Inspector of Prisons Charlie Taylor told the PA news agency that staff shortages are "the source of many problems" at the prison, adding: "Something obviously went wrong in terms of security, and that will come out over time."
Khalife, who was awaiting trial after allegedly planting a fake bomb at an RAF base and gathering information that might be useful to terrorists or enemies of the UK, was discharged from the Army in May 2023.
He has denied the three charges against him.
He was last seen wearing a white T-shirt, red and white chequered trousers and brown, steel toe-cap boots, the Metropolitan Police said. He is described as slim and 6ft 2in, with short brown hair.
Mr Murphy told reporters: "However, he clearly could very quickly change those clothes, so I wouldn't want to focus too much on that."
Kent Police confirmed junctions eight and nine of the M20 were temporarily shut on Thursday due to the enhanced security checks - and to allow freight heading for mainland Europe to queue on the empty section of the motorway.
Mr Murphy previously said there was "no reason to believe Khalife poses a threat to the wider public" but urged people not to approach him and to call 999 if they spotted him.
Khalife has links to the West Midlands and Kingston in London, but Mr Murphy said the hunt was covering the whole of the UK.
He was previously stationed at the Ministry of Defence's Beacon Barracks in Stafford.