Acas, the arbitration service, has issued guidelines advising all employers to remove information that could identify a candidate's age from the main body of job application forms.
The information should instead be retained on a separate form, not seen by selection panels. The guidelines warn: "Asking for age-related information on an application form could allow discrimination to take place."
The advice has been published in the run-up to regulations outlawing age discrimination in employment and training which come into force from October 1. Experts warn that employers that fail to take notice do so at their peril.
Helena Scott, head of policy and research for Age Concern Scotland, told The TES Scotland: "If an employer genuinely wants to operate open and fair treatment for all candidates, clearly any aspect of a person's personal details that might reveal their age, and therefore could prejudice that employer, should be removed from an application form. The Acas guidelines should be taken very seriously indeed."
Brian McKechnie of the senior studies institute of Strathclyde University, who is a steering group member of the Age Positive campaign, warned: "It will only be a matter of time before such a practice forms the basis for a legal challenge that it has resulted in age discrimination."
Professor McKechnie added: "Older teachers who have taken career breaks and want back into their profession, or who simply want to widen their experience by moving post, are often the best type of employee. It is a waste of human potential not to employ them. They should not have their movement restricted because of ageism."
Professor Mike Danson of Paisley University commented: "Education recruitment has been a law unto itself since selection and interviewing is done at school level and few of the recruiters such as headteachers and parents have had equality and diversity awareness training - particularly regarding age."
But a spokesman for the Convention of Scottish Local Authorities said:
"There is no reason why councils should not know someone's age. It will be illegal to discriminate on grounds of age but not to know what age a person is."
The GTC's registration number includes the precise year a candidate completed training and therefore sought to enter the profession. But a spokesman said: "We have no plans to review the current coding. Being registered remains a legal requirement to teaching in Scotland and is in the interests of pupil safety and teaching standards."
A spokesperson for Edinburgh City Council's children and families department said, however, that it did not plan to remove the requirement to ask for the GTC registration number in the main body of application forms for teaching posts.