The warning comes as millions of people are due to being auto-enrolled into a workplace pension scheme, but Altmann warned these would not ensure "adequate retirement incomes".
She called for an overhaul of defined contribution (DC) schemes and said the "future of pensions is more complex and risky than ever before".
Altmann, who is a former investment banker and pensions adviser to the Government, today published a report, which found 60% of pension savers said they do not understand the risks they face in DC pensions.
The report Pensions - Time for change,sponsored by insurance group MetLife, found that figure rises to 75% among 18 to 24-year olds, who are a key target for auto-enrolment.
"New thinking on both pensions and retirement is urgently required," said Altmann. "Those who want the best chance of better incomes will need to plan carefully for the future."
She said the saving schemes were too geared towards people who are set to retire at 65, which is unlikely to happen in the future as the UK has no default retirement age and an ageing workforce.
