A Senate oversight chairman is demanding the federal government finally disclose how much money taxpayers will lose because of the rapid financial collapse of 12 Obamacare health insurance co-ops, the Daily Caller News Foundation has learned.

Senator Ron Johnson (R-WI), the chairman of the Senate Committee on Homeland Security and Governmental Affairs, demanded in a January 19 letter to the Centers for Medicare and Medicaid that federal officials provide a full accounting for the losses. CMS oversees the experimental co-op program.

“The number of failed CO-OPs and the anticipation of additional closures raise concerns how CMS will recoup the $2.4 billion in loans to the 23 CO-OPs,” Johnson told CMS Andy Slavitt, the acting administrator.

The committee estimated that at least half of the $2.4 billion in funds awarded to 23 experimental health insurance co-ops have been lost.

The co-ops were devised by the Obama administration in 2012 as an alternative to commercial health insurance companies. Many were led by inexperienced activists or those with close political ties to the Obama administration.

Last year all but one of the 23 operating co-ops suffered large net operating losses and 12 ultimately closed their doors. A 24th co-op in Vermont was never licensed.

The co-op financial defaults forced more than 450,000 health insurance customers to scramble last year to find new, affordable health coverage.

Maine, the sole co-op that last year reported a positive balance sheet, announced in early December it would no longer sell insurance policies in 2016.

The co-ops that have failed are supposed to “forfeit all unused loan funds” with interest within 60 days of state liquidation, according to the federal law.  

Johnson doubted, however, if any funds will be available to repay the government and slammed he center for its lack of openness and transparency.

“CMS’s oversight of the troubled CO-OP plan has been plagued by a fundamental lack of transparency with the American public and Congress,” Johnson said.

It’s also possible the 2015 run of co-op defaults may not have ended. At least 11 co-ops are under “enhanced oversight” by CMS because of poor enrollment that are facing significant operating losses.

“CMS has reportedly placed 11 operational CO-OPs on an ‘enhanced oversight’ list, but has declined to disclose which CO-OPs it placed on the list or its rationale for doing so,” Johnson noted in his letter.

Slavitt, the CMS acting administrator, has been tainted by ethics charges and accusations he faces a conflicts of interest in the job. He was nominated by President Obama to serve as the new head after Marilyn Tavenner was fired over the failure of the Obamacare launch.

Upon joining CMS Slavitt was awarded a rare “ethics waiver” which permitted him to rule on regulations that could affect his previous employer, United Health Group.

UHG is the largest health insurance company in the country and generates a third of its revenues from the federal government, primarily from CMS.

Johnson asked for original copies of the co-op loan agreements and the standards used by CMS and its accounting consultant, Milliman, to approve the co-ops,

Johnson demanded a CMS response by February 2. But to date, the Center has been slow to respond to all congressional requests over Obamacare.