UNISON said Solent University must immediately pause plans to “shift support staff to an inferior pension scheme”.
Members of the union who work at the Southampton university are said to feel let down by the plans.
It comes after vice chancellor Professor James Knowles announced a proposal to outsource university staff to a subsidiary company, Solent University Services Limited.
This would force staff out of the Local Government Pension Scheme (LGPS) in favour of a scheme with reduced benefits, said UNISON.
However, the university has confirmed that staff employed prior to autumn 2018 are currently part of the LGPS, and those who joined after this time have access to a direct contribution pension scheme via a subsidiary.
Louise Barter, South East regional organiser for the union, said: “Solent’s loyal staff deserve decent pensions, not cuts to their retirement package. We’ve heard from workers who are frightened and angry they may need to change their retirement plans.
“Many have given decades of service and feel utterly let down by the university’s actions.
“One member of staff called it a slap in the face for those who’ve stayed loyal through years of redundancies and poor pay rises.
“Management must pause these damaging plans and work with unions to protect the people who keep this important university running.”
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The changes to the staff pension scheme will mean that workers will be offered a reduced retirement package linked to investment returns.
This is instead of receiving payments linked to salary and length of service.
A spokesperson for UNISON added: “The university has confirmed staff who refuse to transfer to the sub-co will have effectively resigned, with no entitlement to a notice period or redundancy package.”
In response to this concern, the university said this is “very standard” as part of the process used to protect staff jobs.
“Like many universities across the sector, Southampton Solent University is carefully considering a range of measures to ensure our continued financial sustainability and ability to deliver a high-quality education”, a spokesperson said.
They added: “As part of this, and importantly to secure jobs within the university, we are currently carrying out a comprehensive consultation around the proposed transfer of Professional Services staff from the Local Government Pension Scheme to a defined contribution scheme, already available to professional service colleagues since 2018.
“A final decision on this matter has not been made at this time.”