U.S. Sen. Elizabeth Warren accused four insurance companies Thursday of potential securities law violations for making contradictory statements about the Labor Department’s fiduciary rule, claiming it was both unworkable and workable.

In a letter to SEC Chair Mary Jo White, Warren said the four companies submitted comment letters to the Labor Department claiming the department’s fiduciary rule, meant to curb conflicts of interest in retirement advisor practices, would “seriously harm” them and the retirement advice industry.

At the same time, however, she produced statements from top executives at each of the companies last July saying the fiduciary rule would not be burdensome.

The Massachusetts Democrat said the insurers’ contradictions amount to possible law breaking because securities regulations prohibit companies from misleading investors about facts that could affect their business and their stock price.

She is asking for a Securities and Exchange Commission investigation of Jackson National Life Insurance Company, Lincoln National, Prudential Financial and Transamerica Corporation.

The allegations come the week before the DOL is expected to release its final regulations on the rule, which requires retirement plan advisors to act in the best interests of plan participants rather than making recommendations and decisions primarily to add to the advisors’ own wealth.