Sen. Brock Adams says he made an "error in judgment" by allowing a 26-year-old woman to spend the night at his house last year, but he denies allegations that he sexually assaulted her.

"These charges are absolutely false," Adams, D-Wash., told reporters on Tuesday. "I have never had a desire to hurt this woman or her family, and I don't know why they are trying to hurt me and my family."With his wife, Betty, standing at his side, Adams said Kari Tupper, a former congressional secretary whom Adams has known since she was a child, has harassed him for more than a year.

"After the horrible lies didn't work for her, the woman threatened to file a civil lawsuit unless I paid $400,000 in hush money," he said. "Betty and I refused her demands - I will not be blackmailed."

Adams, 61, a former transportation secretary in the Carter administration, said he should never have invited Tupper to spend the night at his house on March 27, 1987, when Mrs. Adams was not around.

"I made an error in judgment that put me in a position where I could be falsely accused," he said. "For that I apologize to my family, friends and the people of the state of Washington."

Tupper was an $18,000-a-year secretary with the House Select Committee on Aging at the time. Now married and living in Seattle, she filed a report with the Metropolitan Police Department on July 24, 1987.

She alleged that the incident took place in Adams' house in an exclusive residential section nearly four months earlier - between 9:15 p.m. on March 27 and 6:30 a.m. on March 28 - according to the report.

Capt. William White III of the District of Columbia police said the allegation of simple assault was investigated. "We consider the matter closed," White told the Seattle Post-Intelligencer, which first reported the story. The U.S. attorney's office reviewed the case but did not press charges.

Tupper could not be reached, and her husband declined to comment.