White House on Wednesday embraced calls for an investigation into whether the government's former Medicare chief pressured a subordinate to sit on cost estimates of last year's Medicare legislation.

Those estimates - higher than those projected by congressional budget analysts - have yet to be made public or turned over to congressional Democrats who have requested them.

White House spokesman Scott McClellan endorsed plans by Health and Human Services Secretary Tommy Thompson to look into the matter. "Obviously it's a serious allegation," McClellan said.

Thompson said Tuesday his staff is gathering the documents.

In an hour-long meeting with reporters, Thompson did not dispute the thrust of a story by The Associated Press in June that Thomas Scully, who ran the Medicare agency until December, threatened to fire his top actuary, Rick Foster, if Foster released his calculations to Democrats.

Scully has said his comments were "heated rhetoric in middle of the night."

But the matter has taken on a new life because the administration projected in the budget it submitted to Congress last month that the 10-year cost of the bill would be $534 billion, instead of $395 billion estimate used in writing the legislation. Foster estimated in June that a version similar to what became law would cost $551 billion, according to a document subsequently obtained and released by House Democrats.

"There seems to be a cloud over this department because of this. We have nothing to hide, so I want to make darn sure everything comes out," Thompson said.

Democrats applauded Thompson's request, but Sen. Edward Kennedy, D-Mass., said questions still remain about why the president, Thompson and other officials continued to say the legislation would cost $400 billion "when their best estimate was that it would cost much more?"

Thompson said administration officials made clear that their financial assumptions about the legislation led to higher estimates. But he said he did not see the final estimated cost until just before Christmas, a few weeks after President Bush signed the Medicare law.

Thompson said he never instructed Scully to prevent Foster from sharing his higher cost estimates with lawmakers, some of whom said they would not vote for legislation that cost more than $400 billion over 10 years.

Scott Whitaker, Thompson's top aide, said he telephoned Foster in June at Thompson's request to reassure him his job was safe.

The secretary placed much of the responsibility for the controversy on Scully, a voluble lawyer and former hospital trade association executive known for his quick wit and sometimes impulsive comments.

Thompson said he should have exercised more control over Scully. "But all of you know Tom Scully. Do you think that's possible?" Thompson said.

Scully did not respond to efforts to reach him Tuesday.

Thompson said the Medicare and Medicaid agency would be run differently under Scully's successor, Dr. Mark McClellan. The Senate confirmed McClellan, now the commissioner of the Food and Drug Administration, last week and Thompson said he expects him to begin his new job this month.