Quality watchdogs have demanded "incisive action" at Luton University before there can be full confidence in its academic standards.
In an audit report published this week, the Quality Assurance Agency says that external examiners at Luton had raised concerns about "weak academic standards" on undergraduate courses. Two examiners warned that "at the lowest level of passing grade the standards at the university did not match those of comparable institutions". But despite this, the examiners had signed off the exam-board decisions and the students had been allowed to pass.
The episode forms part of a catalogue of problems that includes the flawed conduct of examinations, with errors in exam papers and poor exam invigilation.
The agency says that until action is taken in a number of areas, "the general confidence that could be placed in the university's management of standards would have to be qualified".
The QAA carried out its audit of Luton's quality assurance systems in March last year, but publication of the report was delayed by a dispute between the agency and the university about the content.
The QAA report says it is advisable for the university to ensure that "all external examiners are fully committed to the decisions of boards of examiners prior to signing their confirmation to these decisions".
Aspokeswoman for the Campaign for Academic Freedom and Academic Standards said that when externals with well-founded concerns about standards lack the courage and integrity to veto bad decisions, the whole system is invalidated.
Concerns are also raised about the conduct of examinations. Although Luton's internal exams auditor raised "a range of matters which must be of serious concern to the university", the university did not always respond adequately.
The report says it is "necessary" - the QAA's highest level of priority - to ensure the exam auditor's reports are fully acted on in future.
The QAA report also says that the limited language skills of international students risks inhibiting learning opportunities, and the university should ensure that international students are given effective support.
Luton's dean of quality assurance, Richard Harris, said the audit report was "overall a very positive document", with four important areas of commendation.
He said the comments the QAA made about external examiners reflected "a misunderstanding about procedures by two external examiners, since rectified by the production of clearer notes of guidance".
"The external examiners may initially, on receipt of students' scripts, have had reservations about standards," he said. "After the moderating process and the boards of examiners' meetings, both external examiners were happy to sign the class lists, signifying their satisfaction that the standards set by the university are comparable to the standards set elsewhere in the UK."
He said two external examiners' reports out of a total of nearly 200 was "a very small sample from which to draw an inference about the security of an institution's approach to the maintenance of standards".
Mr Harris also said the university considered the QAA's demand for necessary action over the exam auditor's advice was unjustified.