A union representing prison officers says a company running Mt Eden prison in Auckland is not up to the job and should be stripped of its contract.
Two inmates have escaped in the first year of Serco running the prison.
A report into the latest incident found loose handcuffs meant the prisoner was at large for half an hour after a medical appointment in June.
Serco has been fined $150,000 and ordered to make operational improvements.
The Corrections Association says Serco's $300 million contract should be revoked.