A lawyer has sued his ex-wife to try to recover millions of dollars he paid in a divorce agreement that he says was based on their belief they had $5.4 million invested with fraud suspect Bernard Madoff.

He says he later learned the Madoff Investment Securities account was empty.

Steven Simkin says he gave Laura Blank $6.6 million as her share of marital assets in July 2006 after more than 30 years of marriage. That figure included $2.7 million, half the supposed value of the Madoff account.

Simkin, 61, says in papers filed late Tuesday in Manhattan's state Supreme Court that he learned the account was empty, that its valuation "was a sham and a fiction," after Madoff's arrest Dec. 11.

Simkin, of Scarsdale, N.Y., said he also learned from news accounts that Madoff, a former Nasdaq stock market chairman, confessed to his employees and to the FBI that he had committed what appears to be the biggest financial fraud in history.

Madoff, 70, is accused of swindling investors out of as much as $50 billion. He's been charged with securities fraud.

Victims include investment firms, charities, colleges and individuals, including one who killed himself after finding out he had lost $1.4 billion.

Madoff has posted $10 million bail and is under house arrest in his Upper East Side penthouse.

Because of Madoff, Simkin's court papers say, "Laura obtained a windfall and Steven did not receive an equitable share of the couple's joint assets." He says he wants to "reform" the settlement because it is "based on a mutual mistake."

"It remains only fair and equitable for Laura to shoulder her share of that harm," say Simkin's papers.

Blank, also a lawyer and now a Manhattan resident, said Wednesday she had received Simkin's papers but had no immediate comment.

Attorney Harvey Sladkus, who has practiced matrimonial law in New York for more than 40 years, called Blank "a lucky gal."

"She's ahead of the game," he said, adding that she can't be faulted for the crime Madoff is accused of committing. He doubts the agreement will be voided.

Divorce lawyer Eleanor Alter said the outcome may depend on whether it can be proved the $5.4 million was in the Madoff account when the couple divorced.

"If the money was there and he [Simkin] left it in a bad investment, then he loses," Alter said.

She added that if Simkin can prove the money was not there, "then he might have an argument, but I think he still loses."

Alter said one of her clients lost millions in the Madoff scandal after a financial settlement with his ex-wife. She said he's using the Madoff case to get his child support and maintenance payments reduced.