Vice President Dick Cheney’s office was involved in removing statements on health risks posed by global warming from a draft of a health official’s Senate testimony last year, a former senior government environmental official said on Tuesday.

The former official, Jason K. Burnett, made the assertion and described similar incidents in a three-page letter to Senator Barbara Boxer, a California Democrat who is the chairwoman of the Senate Environment and Public Works Committee. He then stood with her at a news conference at which she excoriated the Bush administration.

“History will judge this Bush administration harshly for recklessly covering up a real threat to the people they are supposed to protect,” Mrs. Boxer said.

Mr. Burnett, a lifelong Democrat, resigned in May from his post as an associate deputy administrator of the Environmental Protection Agency and chief adviser on climate to Stephen L. Johnson, the E.P.A. administrator. Mr. Burnett has previously criticized the administration’s climate policies and endorsed and contributed to Senator Barack Obama’s presidential campaign.