A New York City mayoral candidate, who reportedly described himself to a woman he had an online liaison with as a "perpetually horny middle-aged man", has admitted exchanging racy messages with another three women, in an attempt to save his campaign.

Anthony Weiner, a married father of one, called a second press conference to reassure the public that he put lewd internet messages behind him and is ready to run for the chair Michael Bloomberg is leaving in September.

"I don't believe I had any more than three [relations]," Weiner said. "The point is that it's behind me," he added. "I have worked through these things"

However the Democrat added he is still "working with people" to get help dealing with his penchant for X-rated online flirting, although he doesn't believe his pattern of behaviour is an addiction.

In 2011 Weiner, 48, was forced to resign from congress over a similar scandal, as he confessed sending lewd tweets and snaps to at least a half a dozen women.

His wife Huma Abedin, a long-time aide for former U.S. Secretary of State Hillary Clinton, was pregnant at the time.

The fresh scandal erupted after gossip magazine The Dirty posted explicit messages that a young woman, Sydney Leathers, said she and Weiner exchanged over a few months starting in July 2012.

At the time Weiner was preparing his political comeback, with his wife playing a pivotal role in an effort to change public perceptions of him and create an image of a healing marriage.

Earlier this week, Abedin stood by her husband as she spoke in his defence at a joint press conference.

"What I want to say is I love him, I have forgiven him, I believe in him, and as I have said from the beginning, we are moving forward."

However, Leathers, a 23-year-old from Indiana, said she doesn't believe Weiner is a changed man.

"I felt manipulated," Leathers told Inside Edition TV show. "Obviously I felt like he's saying one thing to me, another thing to his wife, saying another thing on the campaign trail. I don't know who the real Anthony Weiner is, I guess."

"I was shocked because I didn't think he would be so foolish as to do the same thing all over again," she said.

According to polls, Weiner was leading the race for the Democrat nomination for New York Mayor before the scandal broke.

"He was making these campaign promises that he had totally changed, and he was a better man now, and he learned from his mistakes, and I have proof that that was not true," Leathers said.

"He once described himself to me as an argumentative, perpetually horny middle-aged man, and that's completely correct".

The top Democrat in the House of Representatives, Nancy Pelosi, said Weiner's behaviour was "reprehensible" and "disrespectful of women," but it was up to him to decide whether he should leave the mayor's race.

In a letter to his supporters Weiner tried to turn attention back on his campaign proposals rather than on his personal troubles.

"This campaign isn't about me. It's about a great city that is beginning to lose its mantle as the Capital of the Middle Class," he wrote. "This race for Mayor isn't about me. It's about you. And I'll never lose sight of that."

Sydney Leathers on Weiner
Sydney Leathers exchanged racy messages with New York City mayoral candidate Anthony Weiner (YouTube)