(CNN) -- A liberal Democratic congressman who came under fire for a lewd photo that briefly appeared on his Twitter account over the weekend told CNN Wednesday that he did not post the image.

Democratic Rep. Anthony Weiner spoke to CNN's Wolf Blitzer a day after a contentious exchange with reporters in which he refused to directly answer any questions about the picture.

On Wednesday he said he had hired a law firm to look into the matter. But he declined to directly answer whether he appeared in the photo.

"Photos can be manipulated. Photos can be of one thing and changed to something else. We're going to try to get to the bottom of what happened," he said. The photo showed the lower body of a man wearing underwear.

A conservative blogger who broke the story has called for a full investigation of what he said was either the hacking of a congressman's account or something Weiner wants to hide.

But Weiner told CNN he did not think such steps are necessary to deal with what he said was internet spam, an issue that many Americans face.

"Just because it happened to Congressman Weiner on his personal account doesn't mean that the taxpayers should pay for an investigation," he said. "I'm going to turn it over to some people who are going to give me advice on what to do next.

"This seems like it was a prank to make fun of my name, the name Weiner. It happens a lot," he added.

Asked whether he was protecting anyone, Weiner replied, "Yes, I'm protecting my wife, who every day is waking up to these insane stories that are getting so far from reality. You know, we've been married less than a year."

He also declined to say what he had written in direct messages to Twitter followers.

"I'm not going to get into how I communicate with people on social media. There was nothing ... inappropriate," he said.

An e-mail that Twitter sent to members of Congress Wednesday lists several online security tips, according to a copy of the e-mail CNN obtained. The message does not specifically mention the photo posted on Weiner's page, but notes that questions about account security have surged recently.

"Some of you inquired today about the security of Twitter accounts," Twitter's Adam Sharp wrote. "While we won't comment on individual accounts, news reports of the past few days are a good reminder of the importance of actively protecting your account credentials."

Weiner on Tuesday told reporters he wasn't interested in talking about the issue any more, saying he already made statements over the Memorial Day weekend after the photo turned up on his Twitter account Friday night.

In a heated exchange with reporters, he repeatedly dodged direct questions about the photo.

"If I were giving a speech to 45,000 people, and someone in the back threw a pie or yelled out an insult, I would not spend the next two hours of my speech responding to that pie or that insult. I would return to the things that I want to talk about," Weiner said in response to a question about whether he sent the lewd photo to a Seattle woman.

He also refused to say why he hasn't asked law enforcement to investigate if in fact his account was hacked, as he has said it was.

Despite repeated efforts by reporters, Weiner did not directly answer questions about the photo.

In earlier comments, when asked if the photo was of him, Weiner deflected the question.

"I'm not going to talk about this anymore," he said, adding: "I'm going to get back to the conversation I care about," including economic issues and what he calls a conflict-of-interest situation involving conservative Supreme Court Justice Clarence Thomas on the health care reform law. The New York Democrat is a leading liberal voice in Congress.

Asked several questions about the Twitter situation Tuesday, Weiner stuck to his message.

"I understand you're doing your job, but I'm going to go back to work now," Weiner said at one point. When asked if he was concerned about being hacked, he responded: "I'm going to return to working on the things I care about. I participated in the story a couple of days now, given comments on it. This is a distraction and I'm not going to let it distract me."

When a reporter noted the distraction might go away if he answered the questions, Weiner answered: "I'm not convinced of that.

"I'm not convinced there's any value of me talking about it," Weiner said.

Asked again if he was the man in the photo, Weiner responded again that he had made previous statements and now it was time for him to get back to work.

On Wednesday, Weiner told CNN that he regretted "the way that I handled it yesterday and I'm trying to do a better job today."

Previously, Weiner blamed the photo on a hacker who got control of his social-networking accounts and played a prank. Weiner's spokesman, Dave Arnold, said Monday the congressman has retained an attorney to look into the situation.

No formal criminal investigation has been launched, which rankles Andrew Breitbart, whose conservative website biggovernment.com first reported the photo on Weiner's Twitter account in connection with a tweet to a Seattle woman.

Breitbart, who has been involved in questionable tactics against Democrats and liberals in the past, told CNN on Tuesday that the case warrants further investigation.

"There's something fundamentally different between a prank and a hack -- a prank is innocuous, a hack is criminal," Breitbart said, later adding he wanted a full investigation by the FBI and Capitol Police.

However, CNN legal analyst Jeffrey Toobin said Tuesday he believed the situation was a harmless prank unworthy of further investigation.

"Twitter is not a very secure environment," Toobin said, noting that information on the site can be unreliable "and doesn't even come from the people it appears to come from."

He added: "There's a famous expression -- don't make a federal case out of it."

CNN's Kate Bolduan, Dana Bash and Rachel Streitfeld contributed to this story.