Approached off the House floor Tuesday, Andrews said only, "It's all false," and declined further comment, referring instead to a statement from his office.
Andrews, who repaid the funds for the Scotland trip and then donated the money to charity, issued a statement earlier Tuesday saying, "I have always followed all the rules and met all the standards of the House."
One of his toughest critics, though, said formation of the new panel indicates that his trouble is getting deeper.
"That means people have decided that you likely have done something seriously wrong," said Melanie Sloan, executive director of Citizens for Responsibility and Ethics in Washington, a nonpartisan watchdog group. "If they're going to clear you, generally this is not what happens."
The announcement cautioned that "the mere fact of establishing an investigative subcommittee does not itself indicate that any violation has occurred."
Under House rules, reprimands or censures of members must first be recommended by an investigative panel, but the subcommittees do not always go that far. In several recent instances, they have stopped well short of such steps or cleared lawmakers of wrongdoing.
"It means the committee has some persisting concerns here after conducting its less-formal review of the evidence," said Rob Walker, former chief counsel to the Senate and House Ethics Committees and now a lawyer at the Washington-based Wiley Rein firm.
Andrews' statement said in part: "I have always responded truthfully and accurately. . . . I will eagerly provide any and all information requested by the committee in response to the false and politically motivated, and in some instances anonymous, accusations."
The subcommittee, like the full committee, has subpoena powers.
The forming of a new panel to dig into Andrews' actions comes shortly after he assumed a more prominent role in the House, cochairing a Democratic policy-making committee. He was appointed by Minority Leader Nancy Pelosi (D., Calif.).
Pelosi's office did not comment Tuesday, noting that she was returning from Rome after attending Pope Francis' investiture.
Questions about whether Andrews crossed a line by making personal use of political funds first arose in 2011 when the Newark Star-Ledger reported on his summer trip to Scotland with his wife and two daughters. Andrews was attending a wedding there. He defended the trip as campaign-related, saying it was a chance to "broaden and deepen" his relationship with the groom, a one-time donor and adviser.
Ethics investigators criticized that explanation and also questioned whether Andrews had violated finance rules by using campaign money to fly his daughter to California - where she had music recording sessions - and for a party that doubled as a graduation party for one daughter and a celebration of Andrews' 20 years in Congress.
"There is a substantial reason to believe that he improperly used" campaign funds, a March 2012 report from the nonpartisan Office of Congressional Ethics said. That panel, though, does not make final determinations.
It instead referred its finding to the Ethics Committee, which conducted a preliminary investigation and voted Feb. 26 to create the subcommittee to continue its work. Its decision was not made public until Tuesday because the full subcommittee had not yet been formed.
Given the clear-cut rules about campaign funds, "it would have been very hard for them to give him a pass," said Sloan, whose group has filed a separate complaint against Andrews with the Federal Election Commission.
There is no timetable for the subcommittee to conclude its work. Any final decision on violations or penalties would come from the full Ethics Committee and, depending on the resolution, could involve a vote on the House floor.
Rep. Trey Gowdy (R., S.C.) will chair the four-person subcommittee. Rep. Pedro Pierluisi (D., Puerto Rico) will be its top Democrat.
Contact Jonathan Tamari at email@example.com or on Twitter @JonathanTamari. Read his blog 'Capitol Inq' at www.philly.com/CapitolInq.