The UK is facing serious labour and skills shortages unless more is done to help the over-50s stay in work, according to a new report.
Older workers face discrimination at work which must be tackled by the government and business, a study found.
Ros Altmann, business champion for older workers, made a series of recommendations, including better back-to-work programmes and training for long-term unemployed older people, as well as improved job centre programmes.
Dr Altmann also called on companies to offer flexible working, breaks and family leave to help older workers combine caring responsibilities with their jobs.
Workers were told not to "write themselves off" when they reach 50 or 60 and to consider part-time or flexible jobs rather than stop altogether.
The report said that by 2022 there will be 700,000 fewer people aged 16 to 49, but 3.7 million more aged between 50 and state pension age.
"If the over-50s continue to leave the workforce in line with previous norms, we would suffer serious labour and skills shortages which simply could not be filled by immigration alone," said Dr Altmann.
"The over-50s are a major untapped resource - a hidden talent pool that can boost output, employment and living standards now and in the future.
"Academic and historical evidence shows that, far from damaging job prospects, keeping more older people in work is associated with rising employment and wages for younger people."
Pensions Minister Steve Webb said: "Beyond the age of 50, people start falling out of the workplace at dramatic rates, but there is a compelling economic and business case for overcoming these obstacles to access this vast untapped talent in the UK labour market.
"The government has made a good start by abolishing the default retirement age and extending the right to request flexible working, but it is clear that old-fashioned and outdated perceptions still persist.
"From next month, we will be trialling targeted and intensive support for older jobseekers, including rolling out an older workers champion scheme across every part of the UK, and we are seeing more firms open apprenticeships up for people of all ages."