Angry that the Bush administration continues to refuse to release all of its documents on the costs of the new Medicare prescription drug law, Senate Minority Leader Tom Daschle (D-S.D.) and House Minority Leader Nancy Pelosi (D-Calif.) penned letters to both President Bush and the Republican leaders of both chambers in their latest effort to get to the bottom of the controversy.

Meanwhile, Senate Finance Chairman Chuck Grassley (R-Iowa) will hold a Members-only meeting Thursday on how and why different Congressional and administration agencies often disagree by wide margins on the cost estimates for pending legislation.

Along with several other high-ranking Democratic lawmakers, Daschle and Pelosi accused Republicans of a “gross abdication of Congress’ constitutional oversight responsibility,” because of the unwillingness of GOP leaders to investigate why Congress was not told that the Bush administration’s estimated cost of the Medicare law was almost $140 billion more than the estimates of the Congressional Budget Office.

The letter asks Bush to respond to several earlier Democratic letters sent in March and May that asked the president to detail his knowledge of the differing cost estimates and identify who among his staff may have been aware of any decision to not inform Congress. The letter to Senate Majority Leader Bill Frist (R-Tenn.) and Speaker Dennis Hastert (R-Ill.) calls on the two leaders to direct their committee chairmen to hold hearings and compel administration officials to testify. It also asks the leaders to “insist” that the Bush administration provide internal documents on the cost estimates and any communications among administration staff, including e-mail, about the estimates and the alleged decision to withhold them from Congress.

The letters to Frist and Hastert remind the two leaders that high-ranking Bush administration officials, including the president himself, repeatedly assured Congress during debate on the bill last summer and fall that the cost of the bill would be no more than $400 billion.

The letter quotes Bush as saying, just days before final passage of the bill in November, that “There’s $400 billion additional dollars available for seniors in this bill.”

The letter also quotes Health and Human Services Secretary Tommy Thompson as saying on Nov. 20, 2003, that, “The president said, ‘You are not going to spend more than $400 billion on this over ten years.’ And the score is going to come in under $400 billion. … We’ve been in conference committee for three months and both Democrats and Republicans use that as the high water marks, saying, ‘We will not go over $400 billion.’”

But the Democrats point to evidence that surfaced earlier this year that the Centers for Medicare and Medicaid had estimated the bill would cost between $500 billion and $600 billion as early as July 2003 and had shared those estimates with White House officials, including Bush’s health adviser Douglas Badger. CMS actuary Rick Foster has alleged that then-CMS Administrator Thomas Scully threatened to fire him if he revealed some of his cost estimates to Democrats in Congress.

Foster’s final estimate of the cost of the law — $534 billion — came out in February of this year to the shock of Republicans and Democrats alike.

Frist spokeswoman Amy Call said it would be “premature to comment” on the Medicare cost estimates and Democratic calls for an investigation in advance of an HHS inspector general’s report due out some time this summer.

With Democrats still smarting over the Bush administration’s refusal to comply with Congressional requests for more information on the differing cost estimates, Grassley said he hoped his committee might be able to get to the bottom of why CMS and CBO disagree so often.

“The purpose is to explore people’s concerns as best we can, and that’ll help us make a decision on having a hearing,” said Grassley.

Sen. Max Baucus (D-Mont.), ranking member on the Finance Committee, said he hoped the meeting would give Members a greater understanding into how CMS and CBO come up with their estimates as well as possibly cause the two agencies to work together more often.

“We might be able to bring the two together a little bit more … and hold their feet to the fire,” said Baucus.

Greg Jenner, the acting assistant secretary of Treasury and George Yin, chief of staff of the Joint Taxation Committee, will also participate in the closed-door meeting, because both have responsibilities for scoring tax legislation under the panel’s jurisdiction.