A private group called Thursday for a criminal investigation into a whistleblower's allegations that one of two companies seeking federal approval to sell silicone breast implants withheld safety information from regulators.

Public Citizen asked the Food and Drug Administration to investigate the allegations raised by a former Mentor Corp. employee. The scientist alleged the Santa Barbara, Calif., company concealed, misrepresented or withheld leakage, durability and other data about its silicone-gel breast implants.

"Unless the FDA opens a criminal investigation into Mentor's failure to submit the studies, it will only encourage Mentor and other device manufacturers to selectively send the agency only those studies that put their products in the most favorable light," said Dr. Sidney Wolfe, director of Public Citizen's Health Research Group.

In a statement, Mentor said FDA representatives visited the company's Santa Barbara facilities in July. "They asked questions and reviewed documents specific to our preclinical testing. To our knowledge, all questions were answered to the satisfaction of FDA," the company said.

FDA will review the letter and respond as soon as possible, said agency spokeswoman Heidi Valetkevitch.

In July and September 2005, the FDA first told Mentor and then Inamed Corp. -- now part of Allergan Inc. -- that it would let them start selling silicone implants once the companies met certain unspecified conditions. The FDA has yet to grant final marketing approval to either competitor. Since a de facto 1992 ban, silicone implants have been used in women only as part of clinical trials.

The former employee first raised his concerns with Mentor last year, but felt the company had no intention of forwarding the information to the FDA. The company then laid off the scientist in May. In June, the scientist contacted FDA officials. In later conversations, the FDA said both Mentor and Inamed had satisfied the requirements spelled out in agency guidelines and that "no further open items would be reviewed," the scientist said in a telephone interview.

Referring to the issues he raised, the scientist said, "Some of them are potentially a problem."

The scientist spoke to The Associated Press on condition of anonymity to not jeopardize ongoing efforts to find work. Wolfe said he confirmed the scientist had worked for Mentor. A Mentor employee with the same name testified about implants to an FDA committee.

The scientist said going public wasn't meant as a retaliatory move against Mentor, but was designed to provide information to the FDA as it reviewed the company's application.

The scientist is the latest of several Mentor whistleblowers to go public with concerns about the company's silicone breast implants. The FDA remains hampered in its ability to probe their allegations, said Diana Zuckerman, president of the advocacy group National Research Center for Women & Families, who says she's interviewed at least five such whistleblowers.

"It's very important to call for investigations, but it is not at all clear the FDA has the resources or the authority to do a thorough investigation to determine whether data are accurate and complete," Zuckerman said.

Silicone-gel breast implants first went on the market in 1962, before the FDA required proof that all medical devices be safe and effective. They were banned in 1992 amid concerns about their safety. At the time, women worried they were the cause of a variety of diseases, including cancer. Alarming cases of ruptures contributed to the concern.

Most studies have failed to find a link between breast implants and disease. But silicone-gel breast implants do not last a lifetime, according to the FDA. A 2000 Institute of Medicine report found rupture rates as high as 77 percent.

Proponents of silicone-gel implants say they feel more natural than do saline implants.