A working rights group has said it will take the government to the High Court over age discrimination legislation to be introduced in October.
New laws aim to tackle ingrained attitudes to older workers
Employees will be able to request to work beyond age 65, but employers do not have to give a reason for refusal.
The Heyday group, backed by Age Concern, will tell the High Court the new law contravenes European equal rights legislation.
Heyday said employers should have to give a reason for refusal.
The government has 21 days in which to submit a response to Heyday's application to the High Court.
If the case proceeds a full hearing is likely to take place in the autumn.
"Taking the government to court is not a step we are taking lightly. Heyday is not a pressure group, but we have to act and the time to act is now," Neil Churchill, Heyday spokesman, said.
"We are determined to challenge the existence and legality of forced retirement."
From October, new rules are being introduced to tackle age discrimination in the workplace.
Employers will be banned from forcing workers to retire before the age of 65.
In order to ensure retirement is not used as cover for an unjustified sacking, company bosses will have to give an individual at least six months' notice of their retirement date.
Workers will also be able to remain in their job beyond the age of 65 if their employer agrees.
While the new laws have been broadly welcomed, lawyers have warned they may lead to a rash of employment tribunals.