What to Know Rep. Dan Donovan says he never used his office to help his girlfriend's son beat a drug charge in December 2015

The congressman, who represents Staten Island and parts of Brooklyn, says he didn't know about the arrest until after the release

He believes GOP challenger and former congressman Michael Grimm is behind the complaint

New York Rep. Dan Donovan is fighting allegations that he used his political power for family gain, and claims GOP challenger and former congressman Michael Grimm is behind the complaint.

The Republican, who represents Staten Island and parts of Brooklyn, is the center of a federal ethics investigation after an anonymous tipster told congressional investigators that Donovan used his political power to help his girlfriend Serena Stonick's son beat a drug charge in December 2015.

Donovan disputed the claim in a news conference Monday as he stood next to Stonick.

"I have never used my office for anything other than the purpose in which I hold it -- to represent the people who sent me to Washington," he said.

He continued, "I never went to the 122 precinct that night. I didn't make any phone calls. I didn't know Tim was arrested until after he was released."

Donvoan says he was in Washington and Brooklyn the day of the arrest.

He believes Grimm is behind the complaint: "I don't know if Michael Grimm is the anonymous source, but someone had to instruct this individual how to file a House Ethics Committee complaint," said Donovan, who's gearing up for a tough GOP primary later this spring.

Grimm responded in a statement to News 4, "Donovan could put this scandal to bed once and for all by releasing his, his girlfriend's and his chief of staff's cell phone records from the night of O'Connell's heroin bust to prove he had no knowledge of involvement in the case."

Stonick's son was charged with possession, not distribution -- a decision that law enforcement made, according to Grimm and Stonick.

"While we know that our lives must be public to some degree, there are certain things that should not be used for political enterprise," said Stonick. "The struggle of an addict is one of them."

Donovan's office is asking the House Ethics Committee to expedite the investigation. He wants to bring the anonymous source forward and have them testify under oath.

The Office of Congressional Ethics told News 4 in a statement that all investigations are confidential.