Half of those claimed it was because they were considered too young, not too old.
The peak age when women felt they had suffered discrimination was 40, while for men it was 51.
According to the survey, one in every six workers who had experienced ageism simply moved on to another employer. While one-sixth of them made an informal complaint, the majority took no action.
The findings seem to contradict the belief that older workers are inflexible. Only one in 10 of older employees said that acquiring new skills would be difficult.
The survey, Towards A Balanced Workforce, was carried out by the Employers Forum on Age and recruitment and communication consultancy Austin Knight.