Unison has condemned the appointment of a private company to run the NHS patient transport service in Suffolk and parts of Norfolk.
The decision comes just weeks after Essex-based Private Ambulance Service, which operated in Bedfordshire and Hertfordshire, went bust, leaving patients stranded and staff unpaid.
Unison regional secretary Chris Jenkinson said it was "beyond belief" that the clinical commissioning groups, which handed out the contract, were prepared to take on a private firm, E-Zec Medical Transport.
In 2014 there were complaints about the service provided by E-Zec in Dorset. At the time it said it was striving to make improvements.
Mr Jenkinson said: "The private sector has shown time after time that it is incapable of running NHS services.
"We cannot continue having our vital public services handed over to the lowest cost bidder in the hope they won't mess it up."
Wayne Spedding, operations director at E-Zec, said the contract showed "our service quality is being noticed in other parts of the country", adding it was the "largest and most consistent private ambulance service in the UK".
Meanwhile, a spokesman for Ipswich and East Suffolk, West Suffolk, and Great Yarmouth and Waveney clinical commissioning groups, said the process to appoint a new provider had been "rigorous and in-depth".