A "silent majority" of academics aged 50 and older feel "undervalued and often superfluous", a survey by the University and College Union will reveal next week.
Sally Hunt, UCU joint general secretary, known for her campaigning on gender issues, is due to mount a surprise call at next week's Trades Union Congress for more support for older workers, who in higher education make up most of the university population and are more likely to be white and male.
She will warn that the pending retirement of thousands of staff in further and higher education could cause "severe difficulties" and damage the quality of education.
The union will be unveiling the findings of a survey of more than 1,000 university staff into age discrimination. It is expected to show that staff who have just started their career (the under-34s) and those approaching retirement (those aged 50 and over) feel most discriminated against at work.
It will show that more staff in the 50-plus bracket would also retire immediately if they had the option.
Ms Hunt is due to speak at a fringe meeting organised by Age Concern, where she will argue that debates on discrimination too often miss out the problem of ageism.
She will say that it is often the "older" workers, aged 50 and over, who are considered first for any voluntary redundancy, which gives them a feeling of being undervalued and often superfluous.
Much more needs to be done for a silent majority of 50-something academics who are unhappy in their jobs, she will argue.
The UCU's motion to the TUC also focuses on age. It says: "Congress notes that by 2014 there will be more people over the age of 65 in the UK than under 16. Research shows that 29 per cent of people have experienced age discrimination, which can be linked to new stresses in later life both at work and at home."
The motion supports the right of employees to work beyond the age of 65 and warns that the "impending retirement of thousands of further and higher education staff will lead to severe difficulties, potentially affecting the quality of the education provided".
The motion says: "Congress therefore calls on the Government to... address further and higher education recruitment and retention problems by ensuring secure funding for competitive salaries and closing the further education pay gap."
It calls on the Government to "amend the Employment Equality (Age) Regulations to offer full protection for people dismissed from employment at or over the age of 65, allowing them to continue working if they are willing and able to do so".