Hillary Clinton told ABC policy what counted to ordinary Americans and Mr Clinton "could not afford to be distracted" by the allegations.

"It's been our experience having lived through the last six years that most Americans are concerned about what their president can do for them."

Mrs Clinton said she would give her husband 100 out of 10 for his State of the Union address on Tuesday evening.

"Not only was it one of the best speeches my husband has given but it had so much solid substance about what he wants to do for the country."

Mrs Clinton previously insisted that the "truth will come out" about her husband's relationship with Ms Lewinsky.

She said he was a victim of a right-wing conspiracy being perpetuated against the president.

She put the furore in personal terms, accusing the independent prosecutor Kenneth Starr of conducting an obsessive smear campaign.

"I do believe that this is a battle," she said on Tuesday morning. "The great story here is a vast right-wing conspiracy who have been conspiring against my husband since he first ran for office."

The scandal surrounding Mr Clinton's relationship with the 24-year-old former White House volunteer shows no signs of abating.

He made no mention of it during his State of the Union address on Tuesday but it continues to overshadow his economic achievements.

Surreptiously-recorded tapes in the possession of Mr Starr appear to show Mr Clinton had sexual relations with Monica Lewinsky when she briefly worked at the White House aged 21.

The sex scandal became one capable of brining down the Clinton presidency because the tapes also suggest Mr Clinton was involved in pressuring her to lie about the relationship on oath.

In a sworn statement to the sexual harassment case being brought against Mr Clinton by Paula Jones, Ms Lewinsky categorically denied all charges.

But since the Drudge Report Internet site reported the existence of the tapes and fuller details were provided by Newsweek magazine on its Web site, the trickle of new rumours has become a flood.

Reports of a witness catching Mr Clinton is a compromising position with Ms Lewinsky and a stained dress seized by the prosecutors have strengthened scepticism about his denial of the charges.

Mr Starr has insisted he has strong evidence against Mr Clinton and rejected Mrs Clinton's suggestion of bias.