The chairman of the East of England Ambulance Service has resigned, a week after it failed a watchdog inspection of its level of care.

Maria Ball, who joined the East of England Ambulance Service NHS Trust 10 years ago, announced her decision to the board on Wednesday with immediate effect. It followed concern about ambulance response times.

Her departure comes as changes to the way the trust is run are expected to be announced next week, as part of a plan which includes devolving powers to a local level. This would mean Essex would have more say in the running of the service.

Vice-chairman Paul Remington will temporarily run the service with interim chief executive Andrew Morgan.

Mr Remington, who will set out the changes next week, praised Ms Ball for overseeing the trust’s formation and “bringing together three disparate organisations into one service” and its later development.

“Maria has spent many years leading the ambulance service and I would like to thank her for her dedication and commitment through some challenging times,” the vice-chairman said. “We now must concentrate on looking forward and focusing solely on how we improve service to patients and better support our staff.”

The Care Quality Commission report said last week that the trust’s ambulance response times had “deteriorated” since March 2012 and “people could not be assured they would receive care in a timely and effective manner”. Mr Morgan has since pledged more frontline staff and ambulances and said the trust was undertaking a review into what resources were needed to meet patient demand.

Gary Sanderson, spokesman for the trust, said it was aiming to improve its performance with measures “including 200 new frontline recruits, 15 extra ambulances … better working with hospitals to tackle handover delays, more effective rotas and the implementation of an organisation development strategy to empower and engage staff”.