NHS experts have been called in to help the hospitals treat patients within 18 weeks of referral after waiting times targets were missed for 12 months in a row.
Almost 6,700 patients had been waiting too long at the end of April.
Mid Yorkshire Hospitals Trust ranked third from the bottom of all NHS organisations required to treat 92 per cent of patients within the timeframe.
Mid Yorkshire, which runs Pinderfields, Pontefract and Dewsbury hospitals, was meeting the target in just 84 per cent of cases, according to figures reported to its board meeting yesterday.
A board report said latest data “shows the trust ranked 183 out of 185 reporting organisations nationally for incomplete RTT (referral to treatment) performance in April 2016.
“The 92 per cent standard was achieved by 130 organisations across England.”
Of the 41,700 patients waiting for treatment that month, 6,689 had been waiting more than 18 weeks.
The number of treatments needed was greater than hospitals had capacity to provide in some areas. In plastic surgery, just 70.6 per cent of patients had been treated within 18 weeks.
The figure was 75 per cent for ear, nose and throat (ENT) treatment and 77.6 per cent for trauma and orthopaedics.
But bosses at Mid Yorkshire hope to improve performance after inviting the NHS Improvement Intensive Support Team to carry out a review in May.
A report and recommendations was due to be discussed at yesterday’s meeting.
A paper to the meeting said: “The Trust has failed to achieve 92 per cent since July 2015. Significant work has been undertaken to understand the causative factors.”
Causes included rising numbers of patients and some treatments being cancelled due to industrial action.
Staff leaving the organisation were also a factor.
The report said: “It is essential that a recruitment and retention programme is introduced, alongside a review of the key skills training.”
Mid Yorkshire is also among trusts which have struggled to meet targets for patients who arrive at A&E to be seen in four hours.
In April, 88.4 per cent were either admitted, transferred or discharged within the four-hour timeframe at the trust, against a target of 95 per cent.
Only eight NHS organisation in England met the four-hour target that month.