South Central Ambulance Service staff 'pushed to the limit'
Staff at an ambulance trust which has missed response time targets five months in a row are being "pushed to the limit every day", its boss says.
National standards dictate ambulances should reach the most serious 999 calls within eight minutes, 75% of the time.
South Central Ambulance Service has not achieved this target since May.
Director of operations Mark Ainsworth blamed a high demand and high turnover of staff. Unison said members were "exhausted" and "leaving in droves".
"We are concerned our staff are being pushed to the limit every day with the demand on our service," he said.
"We are doing all we can to try and improve that," he added.
In October, 70% of ambulances on "red one" calls arrived within eight minutes.
Since the same month last year, South Central Ambulance Service NHS Foundation Trust has hit the target of 75% in four out of 12 months.
Mr Ainsworth said: "One of the issues is the level of staff we have. We have seen quite high attrition rates of our staff.
"We are seeing demand increase year on year."
He said about 40 red one calls were received each day over Hampshire, Berkshire, Oxfordshire and Buckinghamshire.
Red one calls mean the patient has stopped breathing while red two calls mean the patient is in a life-threatening condition.
The target for red two is also eight minutes and the service received an average of 440 of these calls each day last year.
Mr Ainsworth said private ambulance companies were being used over the winter months to cope with demand.
New employees to fill the trust's 200 vacancies are being recruited from UK universities and from Poland and Australia.
Gavin Bashford, a paramedic and branch secretary for the Unison union, said staff were "exhausted and leaving the service in droves".
He blamed late finishes with shifts running up to 14 hours and paramedics' frustration at being sent to relatively minor cases.
"It's to do with the demands placed on staff - happy staff don't look for other jobs," he added.