Word also emerged that the wife he has publicly humiliated is pregnant.
Democrats in Congress, distancing themselves from the once rising liberal Democratic political star, are becoming increasingly concerned about the political fallout.
A House Democratic aide said late on Wednesday, "There are strong signals coming from members that represent a growing concern in the caucus about his actions and you see members speaking out."
Allyson Schwartz, a member of the House of Representatives Democratic campaign committee, made it clear she had seen enough of the scandal that was tarnishing the party's image.
"Having the respect of your constituents is fundamental for a member of Congress. In light of Anthony Weiner's offensive behavior ... he should resign," Schwartz said.
Weiner, 46, who many had seen as the next mayor of New York, is resisting calls he step down for sending lewd photos of himself to women with whom he had held steamy online chats.
"I think his hope and instinct is that he can stick it out," said a senior New York Democrat, asking not to be identified. "We'll see."
But there were deeper questions about Weiner's political future after an explicit photo of the congressman reportedly surfaced on the Internet on Wednesday.
"As Representative Weiner said on Monday when he took responsibility for his actions, he has sent explicit photos," a spokeswoman said in a statement.
"To reiterate, he has never met any of these women or had physical contact with them. As he said, he deeply regrets the pain he has caused. With the full support of his wife, he is working on righting these wrongs with his family and his colleagues," the statement added.
Huma Abedin, 35, an aide to Secretary of State Hillary Clinton, who married the congressman a year ago, is in the early stages of pregnancy with the couple's first child, The New York Times reported, citing three unidentified people with knowledge of the situation.
The Times said the couple had disclosed the pregnancy to close friends and family.
HAS VOWED TO REMAIN IN POST
After vehemently denying for more than a week that he sent a picture of his bulging boxer briefs to a woman in Seattle, claiming he was the victim of hacking, Weiner tearfully admitted to lying about the scandal on Monday.
He also vowed to remain in his post and preserve his marriage to Abedin. Former President Bill Clinton officiated at their wedding last July amid much fanfare that Washington's newest power couple was made of a Muslim, Abedin, and a Jew, Weiner.
House Democratic Leader Nancy Pelosi has asked the House Ethics Committee to investigate whether Weiner violated any of the chamber's rules, and former Democratic Party Chairman Tim Kaine, now running for the Senate from Virginia, said Weiner should step down.
House Republican Leader Eric Cantor on Tuesday became the first top lawmaker to say Weiner should quit.
Dan Ripp of Bradley Woods, a private firm that tracks Washington for investors, said he expected Weiner to quit within days.
"I think he's history," Ripp said. "Democrats aren't giving him the time of day. He has no clout. His own party is looking at him like a bozo. He is dragging them down."