The boss of WA's prisons has admitted weaknesses in the security of prison vans were partly to blame for the escape of a dangerous rapist last week.
Cameron John Graham was just weeks into an 11-year sentence for rape when he was permitted to move closer to his family in the north of the state for Christmas.
It was during his transfer by private prison contractor Serco last Friday that Graham and a fellow prisoner broke out of a prison van, stole a car and went on the run for days - sparking a furious public reaction.
New Corrective Services commissioner James McMahon admitted the reasons for the escape were "procedural and mechanical".
While he refused to detail those issues for security reasons, he said security had been increased.
"I have put directives in place that fix those issues ... and that is important because I need to know I can transport prisoners securely," Mr McMahon said.
Details of the security review came as Serco rejected claims of overcharging, saying an internal audit had found the allegations could not be substantiated.
In a statement released today, Serco said "the cost structures and charges for our services are fixed in our contract, which is publicly available".
Serco has come under considerable criticism since two prisoners, one a convicted rapist and the other an alleged armed robber, broke out of a prison van at Geraldton airport as they were being taken to maximum security prisons in Perth.
Serco Asia-Pacific chief executive Mark Irwin will fly to Perth next week to meet Corrective Services Minister Joe Francis.
Serco said that under its contract, it was paid a set monthly fee to provide "baseline services".
"Where ‘additional services’ are requested the contract requires us to provide quotes to the Department of Corrective Services with a fully itemised estimate inclusive of all direct costs.
"The Department reviews the quotes provided and makes a decision on whether to accept the service or not.
"That decision is at the sole discretion of the Department.
"Once a service has been undertaken the invoice is then reviewed and reconciled by the Department before payment is made.
"Where estimated costs have reduced from the original quote, then the final payment reflects that saving.
"Additional services include medical escorts, funeral and other regional escorts involving movements of more than 50km.
The company said that in the first nine months of 2013 it was paid $518,490 for 170 "additional services".
Most were prisoner transports and movements, with some additional security requests.
Serco rejected claims it had quoted or charged $23,000 for a transport from Geraldton to Carnarvon for a funeral in December 2012.
"The final invoice and cost to the department was $10,367, the majority of which was for an air charter to meet the timing of the funeral, as commercial flights were not available, and then approved by the department," the statement said.
"The original quote for the service was $19,234 (which included the value of services covered by the set monthly fee).
"We have requested documentary evidence to support the allegations which has not been provided and have reviewed the other allegations based on the limited information available.
"We have found nothing to substantiate the allegations. We continue to request more specific information and if this can be provided we will investigate further.
Mr Irwin said the department had been told of the findings of the internal investigation.
“I am proud of our work in WA and our people who deliver essential services. Rightly, the work that we do is subject to rigorous monitoring and review. We will keep working to offer better services and better value for money, but we want to be judged on the facts.”