Health Minister Michael McGimpsey has hit back at claims of poor patient care in the Southern Trust.
The trust has set up a helpline to reassure patients after a consultant claimed they were being put at risk because of a focus on meeting targets.
Southern Trust chief executive Mairead McAlinden denied this and said there was "no evidence" a patient had come to harm.
Mr McGimpsey also rejected claims trusts had ignored clinical priority.
He was referring to further claims that patients being brought back for a review appointment in the Southern Trust were prioritised by the alphabetical order of their surname.
The trust has also rejected this claim.
Mr McGimpsey said he was aware that there had been lengthy waits for some outpatient appointments, particularly for review or follow-up.
"This is unacceptable but the board and trusts are well aware that by March next year, all patients need to be seen in the timeframe determined by their clinician," he said.
"I am confident that they will bring about the improvements necessary to achieve this standard."
He added that he had invested in outpatient services, providing £7.3m last year and a further £6.3m this year.
"This will take time to fix," he said.
He rejected claims made on Wednesday that urgent x-rays had not been reported on in the Southern Trust area.
He echoed a call by Ms McAlinden for staff with concerns to bring them to the attention of senior staff rather than contacting the media.
The deputy first minister Martin McGuinness has criticised Mr McGimpsey's response to the latest series of allegations about health service care, accusing him of a "detached approach".
He added: "I think that he needs to get his act together and recognise that these forest fires, which are breaking out now right, left and centre need to be put out."