Plans for a new system of personal pensions are to be unveiled today by the government.
A White Paper due to today will reveal that from 2012, employees not in an occupational scheme will be enrolled into personal accounts unless they opt-out.
Staff will pay in 4% of their salaries and employers 3%, with an extra 1% from the government in tax relief.
It is estimated up to 10 million workers are not currently in employer-funded schemes.
The idea was proposed by Lord Turner's Pensions Commission to ensure that more people save for retirement.
But the TUC has warned that some employers may put pressure on staff to opt out of the scheme to avoid paying their contributions.
The National Association of Pension Funds (NAPF) has warned that companies with more generous schemes could be tempted to level them down to match the new personal accounts.