This comes after the crew at Boston Ambulance Station sent an open letter to local media saying under investment was putting public safety at risk.

They also stated that management was "hamstrung" by budget considerations.

The Ambulance Trust admits its fleet of 180 vehicles is old, but says 22 new ambulances will be delivered next month and 25 more will arrive next year.

Sell-by date

Staff at Boston said they did not want to alarm the public but felt frustrated by the lack of action.

It is claimed some crew were responding to 999 calls because old ambulances were often off the road being repaired.

Richard Parker of public services union Unison said: "An awful lot of vehicles on the road are past their sell-by date."

Director of Operations at the Trust, Steve West, felt the criticism was unhelpful.

Mixed results

He said: "I think, as a professional paramedic myself, it saddens me that a colleague would make such a statement.

"Every endeavour is made to save life and out response standards show we achieve very high levels of care.

"To alarm the public in this way really disappoints me."

The trust has had mixed results in recent months.

After getting no stars in the latest NHS performance tables, it was then rewarded for fast response times and praised in a patient survey.