Senior leaders at Ulster University (UU) were guilty of a "disturbing lack of governance" during a staff redundancy process in 2016.
Refusing to accept a redundancy settlement offer from a staff union also cost UU an extra £1.4m.
Those are among a litany of failings identified by a UU commissioned independent review into the process.
UU's vice-chancellor offered "a fulsome and wholehearted apology for the hurt and anxiety that was caused".
An industrial tribunal previously found UU guilty of a "serious failure to consult" with the University and College Union (UCU) about 143 staff redundancies it made in April 2016.
After that judgement the university council commissioned Petra Shields, an expert in employment law, to find out what lessons should be learned.
Her report has now been published.
'Little reflection on cost of defeat'
"The overall conclusions are based on findings of governance concerns, emanating primarily from a failure of effective oversight by senior management," it said.
She found the total bill paid by the university to the affected staff as a result of the judgement came to £1.6m.
She said UU had rejected an offer from the UCU seeking £200,000 in compensation to the staff prior to the tribunal hearing as the university believed the tribunal would rule in its favour.
"There appears to have been little reflection on the potential costs of losing, which included the financial costs, the adverse affect on staff morale or the potential reputational damage to the university," she wrote in her report.
Ms Shields was critical of the role of the university's governing bodies - the council and senate - and the senior leadership team.
She said it was "surprising" that no-one on council or senate asked whether the unions had been consulted about the redundancies.
She said both governing bodies had failed to provide responsible oversight.
The tribunal had previously found that the UCU had been "actively misled" by the university's former human resources manager Ronnie Magee.
He left UU in 2016 and declined to be interviewed by Ms Shields for the review.
She said senior leaders at the university had failed "to challenge or monitor" his work "or to carry out senior management's oversight role".
'Difficult time for university'
Her report contains recommendations, including governance training for council and senate members and "basic industrial relations training" for senior leaders at the university.
She also said the university should apologise to the UCU and write individual letters of apology to all affected staff.
The university has said it will do that, accepts the recommendations of the review and acknowledges the errors in its findings.
In an open letter to staff, the vice-chancellor Prof Paddy Nixon said he personally accepted responsibility for his role in what had been "a very difficult time for the university".
"It is very clear there were fundamental flaws in the way this process was managed, particularly in the way that the university engaged with staff and union representatives," he said.
"I am deeply sorry for any stress that has been caused.
"I sincerely value all my colleagues at Ulster University and I deeply regret that this process fell far short of reflecting the esteem in which I hold you and the respect you deserve.
"I can reassure all staff that the senior leadership team and I will act to ensure this never reoccurs."
The University and College Union (UCU) welcomed the report but said it made it difficult to have confidence in the Vice-Chancellor moving forward.
The President of UCU at Ulster University Lindesay Dawe said the report was deeply worrying.
"The report identifies serious failures amongst all senior levels at the University," he said.
"The question must now be what accountability processes will the University implement for those responsible?"