An independent ambulance service used in the region has suspended offering urgent care after it was hit with a long list of issues by health inspectors, including finding bodily fluids on equipment.
It comes as the Care Quality Commission (CQC) issued a warning to all independent ambulance services over safety, after its inspections to date found significant concerns.
And the union representing East of England Ambulance Service NHS Trust (EEAST) staff encouraged a move away from the use of private providers.
A CQC report released last week found listed 14 concerns about Thames Ambulance Service including 'widespread issues with infection prevention, cleanliness and hygiene [...] including bodily fluids on equipment'.
Thames was one of eight independent services used by East of England Ambulance Trust (EEAST) over the four year period of 2012/13 to 2015/16, and was the second most-used provider with 28,310 assignments.
This was beaten only by St John's Ambulance, which had 31,290.
Over those four financial years, independent ambulance services were used by EEAST 134,437 times.
Other problems raised by the CQC about Thames included the use of out-of-date equipment and reuse of single-use items.
As a result of the CQC inspection, Thames voluntarily suspended the urgent care aspects of its service until improvements were made.
Thames had been used less by EEAST in recent years, and was the fourth most-used provider in 2015/16.
However, safety concerns were also reported at Private Ambulance Service, the most-used provider for 2015/16.
The CQC inspection on August 2 found problems with infection control and hygiene, equipment and medicines management.
But these were reported to have been dealt with by the time the CQC returned on August 12.
A spokesman from EEAST said they were not currently using Thames or PAS. He added: 'We use private ambulance services as a flexible resource to meet levels of high demand, particularly over the winter months.
'We have experienced a decrease in demand over the last few months and continue to increase our own front-line staffing, which has enabled us to reduce our usage of private ambulance services.
'Like the vast majority of UK ambulance services, we use Care Quality Commission (CQC) registered private ambulance services so that we can respond to patients as quickly as possible. Alongside the requirement to be officially CQC accredited, each provider we use is also subject to our own internal approval processes and regular quality reviews.'
But Fraer Stevenson, Unison's branch secretary for the trust, said independent providers do not provide the same level of service as an NHS trust.
She said: 'Unison would like to see commissioners and the ambulance service working together to invest in the retention and recruitment of NHS staff and move away from reliance on private providers. This is the sustainable and progressive way forwards that would benefit patients and communities.
'Private providers should not be seen as a way to provide services more cheaply, at the cost of patient safety or care. Money should be reinvested in care and not used to line the pockets of shareholders.
'Private providers are not subjected to the same scrutiny as NHS trusts in relation to the Freedom of Information Act and it's often very difficult to evidence concerns raised by patients. The CQC committing to snap inspections is welcome news.'
Independent ambulance providers (including charities and private businesses) mainly offer specialist patient transport services and non-emergency responses, often on behalf of the NHS. In addition, some provide 999 emergency responses during peak demand.
But in January, it was found between November 2015 and October 2016 EEAST's spending on this has rocketed from around £341,000 per month to £1.4m.
However figures for the same 12 months showed no improvement in Red 1 calls and only a marginal improvement in Red 2. Red 1 and Red 2 calls feature the most seriously ill and injured patients – all ambulance trusts are expected to reach these in eight minutes or less in 75pc of cases.
An EEAST spokesman said: 'We've got some immense efforts going into recruiting more people to patient-facing roles so that our use decreases further wherever possible.'
The CQC has carried out 70 comprehensive inspections of independent ambulance services since April 2015, which covers around a fifth of those registered.
From many of these inspections, CQC has identified common concerns around poor medicines management, cleanliness and infection control practices and a lack of appropriate recruitment checks.
The CQC has published 39 reports on these inspections to date. Within these, the CQC has taken enforcement action and issued 'requirement notices' to 25 different providers, ordering them to improve. This includes two cancellations.
In a letter sent to all independent ambulance providers in England, the CQC highlighted its emerging concerns and reminded providers of their commitment to provide safe and effective care. They also warned those that have not been inspected yet, that they will be scrutinised in the same level of detail.
PAS did not reply to a request for comment.
Thames declined to comment.
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