David Whiting quit today as boss of the organisation after three and a half years in the job.
Yorkshire Ambulance Service (YAS) NHS Trust confirmed he had tendered his resignation and stepped down.
Mr Whiting, who joined the service in February 2011, said in a statement: “Yorkshire Ambulance Service has much to be proud of with a fantastic team of dedicated people committed to delivering the best possible services for patients whilst leading the country in terms of results for patients in major trauma and cardiac arrest survival.
“I have been proud to lead the organisation and, with new challenges and exciting opportunities ahead, I believe YAS will benefit from a change of leadership bringing fresh ideas and insights to keep YAS moving in the right direction.
“From a personal point of view, I feel it is also right for me to pursue new challenges and opportunities.”
Under Mr Whiting’s leadership the ambulance service has seen a string of strikes by members of the Unite union in a row over patient safety.
Unite was de-recognised by YAS for bargaining on behalf of its members at the beginning of last year.
The union claimed patient safety was being put at risk by plans to send semi-skilled emergency care assistants to 999 call-outs.
Terry Cunliffe, Unite’s regional officer, said: “This is not a time for recriminations, but a time to rebuild the service for the benefit of patients and staff.
“We see this as a new chapter opening up and Unite is determined to play a constructive role in this renewal process.
“Unite will be seeking an early meeting with the new chief executive when he or she is appointed for talks to rebuild the service.”
Rod Barnes, Yorkshire Ambulance Service (YAS) deputy chief executive, will step into the role on an interim basis while a permanent replacement is found.