In a report, it said if a worker saves at the minimum contribution rate of 8% throughout their working life, they will have a less than 50-50 chance of achieving an adequate retirement income. This is defined as enough to replicate pre-retirement living standards.
The study, What level of pension contribution is needed to obtain an adequate retirement income, found that a 22-year-old to have an adequate, they needed to save 12% of their earnings. The average amount is around 9% of earnings.
Chris Curry, PPI director, said: "Individuals will need to contribute more than the minimum level at which they are likely to be auto-enrolled to have a good chance of achieving adequate retirement income."
Tom McPhail, head of pensions research at Hargreaves Lansdown, said there are some "relatively simple" measures employers could take to improve workers' retirement savings.
"We have to talk to people about their savings, he said. "The employers with the lowest opt-out rates are the ones that have made the effort to explain to employees what was going on.
"Everyone needs to be able to take responsibility for their own retirement, otherwise they will end up working on into their seventies."