Sessions also asked for information about the role that Jack Lew played in this omission when he was OMB director, and warned that Lew's confirmation to lead the Treasury Department could be at risk.
"As noted in prior years during this Administration as well as during the previous Administration, the Executive Branch considers the requirement to submit legislation in response to the Medicare funding warning to be advisory and not binding, in accordance with the Recommendations Clause of the Constitution," Zients wrote.
At the same time, Zients said the administration takes seriously the Medicare funding gap. He pointed out that Obama's 2013 budget proposed Medicare savings, and that the 2010 healthcare law also addressed Medicare's viability.
"The Medicare Trustees have noted that the Affordable Care Act reduces the need for general revenue financing of Medicare and improves its long-term solvency," he wrote.
In a letter sent Thursday, Sessions dismissed Zients's letter by saying it failed to provide the Senate with any information about Lew's role related to the Medicare trigger.
"The Administration remains in a state of noncompliance with the requirement to send legislation in response to the Medicare Trustees' funding warning," he wrote.
"As our oversight letter states, in order to properly consider Mr. Lew's nomination, Congress will need documents pertaining to his role in the violation of his law, as well as a concrete legislative proposal that brings the Administration into legal compliance. Failure to do so could make it difficult for Mr. Lew's nomination to move forward."
Sessions added that he was "stunned" that Zients would suggest that the 2010 healthcare law "in any way satisfies the legal conditions of the trigger," since the funding warnings continued to be issued even after passage of that law.
"Your reply to the letter from out committee members was non-responsive," Sessions wrote. "The Administration has never complied with the Medicare trigger — and you effectively conceded as much in your letter."