Mascaro, R-West Jordan, 62, adamantly denies he behaved inappropriately and alleges the college-age intern made advances toward him. He says the release of the material is retaliation for his signing an ethics complaint against another House member last week.
"This is absolutely not true," he said.
The letters of apology to the intern and her school, along with a report on the incident, were obtained Thursday by The Salt Lake Tribune under an open records request. The name of the intern was withheld.
The March 13 letter from Curtis to the intern describes a meeting a day earlier with the speaker, Mascaro, legislative counsel Gay Taylor and Michael Christensen, director of the Office of Legislative Research and General Counsel.
"The Representative asked that I apologize to you, on his behalf, for the situation that caused you such discomfort. He was genuine in saying that he never intended any threat or discomfort to you," Curtis wrote.
"I have not yet imposed further discipline," Curtis wrote, "but would consider that if . . . you think additional actions are necessary."
According to a March 5 report filed with the legislative counsel's office, the intern reported Mascaro had made a remark to the intern on Valentine's Day about the sexual prowess of older men, invited her into his office and stroked her hand.
As they stood up to go, "he was right in front of her and his belly was against her. He started rubbing both of [her] shoulders and down her arms as he was facing her." She said Mascaro recognized he was making her nervous, her phone rang and she left his office.
"She asked that after the session, we inform Rep. Mascaro of these facts and warn him about sexual harassment and the political and moral danger of his behavior," the report states. It goes on to say the intern did not want any publicity and "was probably not going to file a lawsuit."
Mascaro tells a very different version of events, which he says also should have been made public.
"She left some really interesting parts out and the story is significantly different with respect to the parts she left out," he said.
He said he agreed to talk to the intern because she was distraught and potentially suicidal and suggested she might take pills. In his office, Mascaro said she told him about an encounter with an older man and that she prefers older men.
Mascaro said he was married. She said that hadn't stopped her professor, at which point Mascaro said he took her by the arm and told her she needed to leave.
"All that other stuff, that hugging and all that stuff is a bunch of crap," said Mascaro, who had not seen her version of events until Thursday at the same time it was released to The Tribune.
The intern, whom The Tribune chose not to identify, said in an interview that Mascaro's version of events is not accurate. "I don't agree with his story," she said.
Rep. Greg Hughes, R-Draper, said the allegations are serious, and should be thoroughly investigated, potentially by the House Ethics Committee.
"I'd like to give my colleague the benefit of the doubt, but given its nature, it deserves to be looked into and resolved one way or the other," Hughes said. "I think sexual harassment is a pretty serious thing, and if there's any substance to it, which it sounds like there is some substance to it, resolving this would be in the best interest of the whole body."
Last week, Mascaro and Rep. Sheryl Allen, R-Bountiful, signed onto a request for an ethics investigation into whether Rep. Mark Walker, while running for state treasurer, made an unlawful job offer to convince his opponent, deputy treasurer Richard Ellis, to drop out of the race.
Mascaro said it is clear that the release of the four-month-old material just four days before the Ethics Committee will open its inquiry into the Walker matter is not coincidental.
"I think everyone knows why it shows up now. There are people that are not happy that I and Sheryl Allen filed this complaint," Mascaro said.
Allen said it was "odd that no legislator knew anything about this and this was kept private until now."
* Claim: A lawmaker was accused of inappropriate behavior with an intern, including sexually suggestive language and touching, prompting the House speaker to apologize.
* Counter claim: The legislator denies the allegation. He says the timing of the public release of the allegation, days after he helped initiate an ethics probe against a colleague, exposes a motive of retaliation.

