Many employers risk falling foul of the anti-age discrimination law because they have not altered their recruitment advertisements in light of the new regulations.
An analysis by Personnel Today of the appointments sections of two leading Sunday newspapers on 1 October - the day the law came into force - showed at least 12 firms were open to discrimination claims after stipulating the number of years' experience necessary for roles.
The job ads ranged from managers to directors across numerous industry sectors, including senior positions in banking and insurance, the oil industry and the NHS.
Some had been designed by executive recruitment firms.
The regulations ban age discrimination in terms of recruitment, promotion, training, provision of benefits, as well as all retirement ages below 65, except where it can be objectively justified.
The current upper age limit for unfair dismissal and redundancy rights has also been removed.
Legal experts warn that specifying an age range for applicants should be discontinued as this will be unjustifiable, except in very rare cases.
Warren Wayne, employment partner at law firm Bird & Bird, said specifying the number of years' experience needed for a particular role could represent indirect discrimination unless it can be justified.
"If there is a different way of specifying your needs, such as referring closely to the particular types of experience and skills, this approach should be adopted," he said.
Wayne added that this would remove the burden of managers having to justify job ads to their HR department every time they tried to recruit anyone.