Disgraced politician Anthony Weiner broke down in tears in court as a judge said she would "make a statement" by sentencing him to 21 months in prison for sexting an underage girl.

Mr Weiner, who was found to have sent explicit pictures to a 15-year-old via Skype and Snapchat, pleaded guilty to transferring obscene material to a minor.

The former New York Congressman had hoped to avoid jail time, after the judge acknowledged he had been receiving treatment for sex addiction.

However, US District Judge Denise Cote said she felt compelled to make an example of Mr Weiner due to the high profile nature of the case.

"Because of the defendant's notoriety, there is intense interest in this prosecution. This is an opportunity to make a statement that can protect other minors," she said.

Judge Cote also noted that he had persisted in exchanging explicit images with women even after his actions were made public.

She said that “despite two very public disclosures and the destruction of his career on two occasions, he continued with the activity.”

Weiner "has a disease", she said. "He has a compulsivity. Some say a sex addiction."

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“I was a very sick man for a very long time, but I‘m also responsible for the damage I have done”, Weiner told the court.

“I acted not only unlawfully but immorally, and if I had done the right thing, I would not be standing before you today.

“The prosecutors are skeptical that I have truly changed and I don’t blame them“I repeatedly acted in an obviously destructive way when I was caught.”

The 53-year-old apparently leaned forward in his chair sobbing as the judge read out her sentence, and left the court without speaking to any reporters.

His lawyer, Arlo Devlin-Brown, said: "We are of course disappointed that Anthony was sentenced to prison, particularly so given that Judge Cote found that the treatment program Anthony had engaged in for the past year was showing great promise and should be continued."

The sexting scandal is question is the third Weiner has faced since 2011. In 2013, his bid to be mayor of New York was scuppered after the media obtained pictures he had sent to a 22 year old woman.