The US ambassador in Nigeria sent a letter to the speaker of the House of Representatives accusing some lawmakers of attempted rape and soliciting sex workers while on a visit to the US at the invitation of the US government.
But the lawmakers have denied the allegations and have threatened to sue the US government for character assassination.
Ten lawmakers were invited to the International Visitor Leadership Program held between 7-13 April in Cleveland, Ohio, and three of them were accused of gross misconduct.
In the letter, Ambassador James Entwistle said the Department of State had reports from employees of the Cleveland hotel that lawmaker Muhammed Gololo had allegedly grabbed a housekeeper in his hotel room and solicited her for sex.
Two other lawmakers allegedly requested hotel parking attendants to assist them to solicit prostitutes, the letter said.
In a response to the speaker of the House of Representatives, Mr Gololo dismissed the allegation as "totally false, baseless and unfounded".
"I categorically deny that any such incident happened," he added.
Mr Goloo said he was demanding an apology from the US government over the allegations or would take legal action to clear his name.
When the BBC contacted the US embassy in Nigeria for comment, its spokesman Sean McIntosh said: "We do not comment on private diplomatic correspondence."