Chartered_bldg The future of Chartered Health Plan and its downtown building are very much in doubt. (Mike DeBonis/The Washington Post)

Updated 1:45 p.m. with no comment from Nathan’s office

D.C. Chartered Health Plan, the city’s dominant Medicaid contractor, might be out of the health-care business within weeks. But it could be left on the hook for as much as $45 million in unpaid medical claims even after the bulk of the company’s business is sold to the AmeriHealth Mercy Family of Cos.

A D.C. Council member is renewing calls to hold Chartered’s owner, businessman Jeffrey E. Thompson, liable for any claims that cannot be paid once Chartered’s remaining assets are sold.

In a Thursday letter to Attorney General Irvin B. Nathan, longtime Thompson critic David A. Catania (I-At Large) urged the city’s top lawyer to “pierce the corporate veil” — a suggestion Catania first made at a February breakfast meeting with Mayor Vincent C. Gray and attended by Chartered receiver Daniel L. Watkins.

Should Chartered be unable to pay the leftover claims out of its post-sale assets — which is not unlikely, considering a huge chunk of the company’s balance sheet represents an unsettled claim with the city that is now under litigation — either health-care providers would have to absorb the costs or the city could pay the claims, even though it already paid Chartered to pay those claims.

“Either option would be unfair and, in my opinion, unacceptable, especially when we have already paid Chartered handsomely to assume these responsibilities,” Catania writes.

Piercing the corporate veil” to hold an individual liable for a corporation’s actions is a complicated undertaking in American jurisprudence that requires proving to a court that a company’s interests are deeply intermingled with those of its dominant shareholder. Catania, in the letter, sets out a number of arguments for finding that Thompson maintained an “adverse domination” of Chartered.

Catania has requested that Nathan respond within a week as to whether he plans to consider pursuing Thompson personally. A spokesman for Nathan declined to  comment Thursday, and three lawyers who have represented Thompson in personal and business matters did not immediately return e-mails for comment.