Jennifer Levitz reports on Congress.

In the past 12 months, more than a half-trillion dollars have “evaporated” from 401(k) plans as a result of turmoil in the financial markets, said U.S. Rep. George Miller, chairman of the House Education and Labor Committee.

Miller made the statement at hearings he called to look at the impact of the financial crisis on U.S. workers’ retirement security.

Lawmakers have been suggesting they may look at policy changes to 401(k)s — the tax-advantaged plans that are the most widely used retirement vehicle — in coming months.

Miller made it clear he sees flaws in the 401(k) model. About $3 trilion is invested in the plans, the majority of it placed in equity mutual funds that track the stock market.

Miller said the 401(k) approach is a policy “not well devised” for changes in the market. He said the plans were meant to be savings vehicles, not primary retirement plans.

Also at the hearing Tuesday, Paul Orszag, director of the Congressional Budget Office, said while traditional pension plans lost 15% over the past 12 months, losses in 401 (k) plans were worse. Orszag said “exposure to broad market risk is unavoidable,” even for 401 (k) participants who have diversified portfolios.