A pending Department of Labor rule that imposes a stricter standard on the advice provided on retirement accounts could swell the assets in 401(k) plans by discouraging rollovers to individual retirement accounts, according to a recent report from research firm Cerulli Associates.

The DOL's fiduciary rule will require that advice on retirement plans be in the best interests of the plan participant, which is stricter than the current standard that advice be suitable. Cerulli said the new rule puts at risk almost half of the assets it expects to be rolled over into IRAs.

If participants in a company's 401(k) aren't being advised to move their assets into an IRA, or if the pluses and minuses of rolling their assets over into an IRA are presented more clearly, "we'd expect to see some more money remaining in the plan," said Rob Austin, director of retirement research at Aon Hewitt.