Emails from School of Music academics to senior management painted a picture of a school in industrial turmoil well before Professor Tregear's unexpected departure last month.

In December last year, the National Tertiary Education Union was made aware of a staff appeal to senior management to support a long-term vision for the school and to support existing staff and, in particular, Professor Tregear.

Professor Tregear was brought in in 2012 to run and restore confidence in the school after Vice-Chancellor Ian Young instituted dramatic staff and budget cuts. He left suddenly last month with 18 months still to go on his contract.

He has just been offered a Senior Teaching Fellowship at Royal Holloway, University of London, one of the top three tertiary-level music schools in the United Kingdom – and is expected to take up the position at the end of the month.

But a number of his former colleagues at the ANU School of Music remain deeply troubled by his treatment during his three-year term, saying he was pushed out by university management after trying to protect demoralised staff from unacceptable workloads.

Vice-Chancellor Ian Young told upset students and staff during a crisis meeting over the future of the School of Music last Thursday that it was regrettable that Professor Tregear had chosen to leave the school.

Deputy Vice-Chancellor (Academic) Marnie Hughes-Warrington also told the meeting she had only become aware of the staffing crisis in May when she became personally involved - only to discover a range of "quality assurance issues" that needed to be dealt with as a matter of priority.

In December 2014, senior managers within the College of Arts and Social Sciences were informed by School of Music staff that there were possible mental health implications of working conditions at the school and that stress levels were extremely high, while morale had plummeted. It was noted that Professor Tregear was under particular strain in trying to keep the school operational amid apparent management indifference.

The NTEU's ACT division secretary Rachael Bahl said "it is disingenuous for university management to suggest that they were not aware of the highly stressful work environment at the School" and the union was currently supporting a number of members at the institution.

" The union has received reports of issues for at least the last year and management should be well aware of the resulting stress leave and workplace health and safety claims at the school. These claims, along with the staff churn at the school, suggest a failure of management to support staff and provide a safe workplace at the School of Music," she said.

Four out of eleven school of music staff have taken stress leave and two have left over the past year. Meanwhile, further staff losses will need to be accommodated with additional staff expected to announce their resignation from the School of Music in coming weeks.

Students and staff were last week concerned to hear Professor Young back away from any historical commitment to employ 13 full-time academic staff to run the school - despite this being the figure published in its Change Management document in 2012, when 16 of the 24 staff were originally axed.

Professor Young said that subsequent student numbers did not sustain that level of staff, although he did concede a "minimum" number of staff needed to be determined in light of the current difficulties facing the school. Staff numbers have fluctuated within the 7-11 range since 2012.

One existing staff member who did not want to be named for fear of reprisals said it was a vicious cycle, whereby staffing uncertainty had led to reputational damage and student numbers dropping and vice versa. Student numbers this year dropped to an historic low of 30.

At last Thursday's meeting, management did commit, however, to reviewing current staffing levels under the guidance of acting Head of School Dr Royston Gustavson.

An international headhunt was also on to fill the role of a permanent head of school.

In March, a group of concerned School of Music academics wrote to the College to question the sudden move of the School of Music Manager to another research school and the impact this would have on administrative processes within an already understaffed school.

They also expressed their concern over the apparent freezing out of Professor Tregear from decision-making processes while he was taking research leave, during which time he was specifically kept out of important all-staff communications at the request of another senior manager.

The academics did not believe this constituted proper university practices and alerted the National Tertiary Education Union "for the sake of full disclosure".

They noted "The head of School has also been omitted from invitations to certain events, including those related to the 50th Anniversary of the School of Music – a significant milestone in our history."

"We can only presume this is a mistake or an oversight of sorts," the academics said.

Professor Tregear was subsequently reinstated into all-staff communication.