Separately, several media outlets reported that Weiner's wife - Huma Abedin, a top aide to Secretary of State Hillary Rodham Clinton - is pregnant with the couple's first child. Abedin is traveling with Clinton on an official trip to the Mideast and Africa.
The statement from Schwartz, who is in charge of candidate recruitment and member services for the Democratic Congressional Campaign Committee, was interpreted as a strong signal that the party leadership wants Weiner out of the House - and out of the way.
Schwartz said she did not talk to colleagues about the issue before making her statement. The House is not in session this week and Schwartz was away last week mourning the death of her father.
"I had a very individual, personal reaction," she said. "Maybe it's because I was hearing about it as other Americans were hearing it, unfiltered by conversations with colleagues."
Weiner, in his eighth term representing a district in Brooklyn and Queens, has made no comment since saying at a news conference Monday that he would not resign.
At the news conference, Weiner admitted to sending a photo of his bulging underpants to a woman on Twitter - after saying for nearly a week that his account on the social-media service had been hacked. That photo was unearthed and first reported by Andrew Breitbart, a prominent conservative blogger.
Weiner also said he exchanged messages and photos of an explicit nature with about six women over the last three years.
The controversy has dominated the news and deflected attention from the debate over the nation's debt limit, as well as Democrats' efforts to batter Republicans for proposing to privatize Medicare.
House Democratic Leader Nancy Pelosi formally requested an ethics inquiry to determine whether Weiner broke House rules. No Democrats have come to Weiner's defense publicly.
Tim Kaine, the former Democratic National Committee chairman who is running for the Senate in Virginia, also said Weiner should step aside. "Lying is unforgivable," he told WCAV-TV in Charlottesville on Tuesday. "Lying publicly about something like this is unforgivable and he should resign."
Weiner, an aggressive spokesman for the liberal view on cable TV shows, has long harbored ambitions of being mayor of New York.
Former Pennsylvania Gov. Ed Rendell also said Weiner should quit, and suggested he get mental-health treatment.
"What I think Anthony Weiner should do is, he still has a lot to offer, he should resign, he should get treatment - and I mean real treament, maybe in-patient treatment," Rendell told Chris Matthews on MSNBC's Hardball Wednesday evening.
"If he can rehabilitate himself, can he someday down the road in New York run for office? Maybe, maybe. But he's got to resign. He owes it to the party, he owes it to Congress, and he owes it to the issues he fought for."
Contact politics writer Thomas Fitzgerald
at 215-854-2718 or email@example.com. Read his blog, "The Big Tent," at www.philly.com/bigtent.
Staff writers Alia Conley and Bob Warner contributed to this article, which also includes information from Inquirer wire services.