HOUSTON, Nov. 16 -- Enron Corp. executive Sherron S. Watkins has resigned, 15 months after sending memos warning Kenneth L. Lay, who was then the company chairman, that improper accounting could cause the company to "implode in a wave of accounting scandals."

Watkins, a vice president of corporate development at Enron, resigned voluntarily, a company spokesman said. Watkins's lawyer, Philip H. Hilder, said she has helped handle bankruptcy matters for Enron, but that her work volume dwindled over the past several months.

In January, a congressional committee revealed that Watkins had written the memos to Lay in August 2001. The company filed for bankruptcy protection Dec. 2 after revelations about years of inflated profits and hidden debt.

Watkins, 43, plans to start a consulting business focused on corporate compliance issues, Hilder said. She was also working on a book about Enron's demise and plans to continue to give talks about her experiences and business ethics.

Testifying before Congress, Watkins blamed the company's collapse on former chief executive Jeffrey K. Skilling, former chief financial officer Andrew S. Fastow and others, and on the failure of Enron's outside auditors to call attention to questionable accounting.

Watkins defended Lay, saying she believed that Skilling misled Lay and that the accounting intricacies she tried to point out were over the chairman's head.

Skilling disputed her claims in testimony to Congress.

Watkins found the accounting problems while working for Fastow, who was indicted last month on charges that he masterminded complex financial schemes that enriched him and helped doom the company.