A convicted British paedophile has been sentenced to 85 years in an American prison for running an online exchange of child abuse images while he was on probation.

Domminich Shaw used the unprotected wireless internet connections of his neighbours in west London to traffic in dozens of videos and pictures of babies and toddlers being sexually abused. He also discussed a plan to kidnap, rape and murder a child.

Shaw, 35, began trading the material almost immediately after being released from a three-year prison sentence in the UK in 2008 for sexually assaulting four young girls, prosecutors said, raising questions about the supervision of British sex offenders.

Prosecutors said Shaw was “among the worst offenders involved in child pornography trafficking ever encountered by United States law enforcement” and they had requested a 570-year sentence. “No such person should be walking the streets,” they said.

He was sentenced this week by a federal judge in Indiana after pleading guilty to 26 charges including conspiracies to receive, distribute and advertise child abuse images. He was extradited from the UK in December 2014.

“Shaw was in every measurable respect the kingpin and primary promoter of sexual violence and abuse involving tragically young and vulnerable children” in his online circle of paedophiles, according to a court filing by the US government.

He operated under the online name “Nepi”, an abbreviation of nepiophelia – sexual attraction towards babies and toddlers. He created and administered a website called “Nepi’s Kingdom” where paedophiles could download abuse images.

Material also distributed from Shaw’s email account was described in horrific detail in court filings. One email sent from his account to more than 60 people contained links to 13 child abuse files, including a video showing the rape of a baby girl. “I know most of you like older than me so heres a little something to make you all happy,” the email said.

Investigators were led to Shaw’s account in 2010 by emails they found in the inbox of David Bostic, a paedophile in Indiana and “key trading partner” of Shaw who was distributing child abuse images he had produced. Bostic has since been sentenced to 315 years in prison. About 3,000 emails, most relating to child abuse imagery were found in Shaw’s account.

Shaw also struck up an online romance with another child abuse contact who was posing online as a woman, according to prosecutors, and the pair discussed a “plan to kidnap, rape and murder a child once he got off supervision”.

Officials at the UK’s child exploitation and online protection center helped the FBI find the internet connections used to access Shaw’s email account. They confirmed boasts made by Shaw in emails that he was “stealing such access from neighbours”, according to prosecutors. In another he complained about having to attend sex offender counselling.

Shaw’s home in London was raided by the Metropolitan Police in January 2011. Officers found on a laptop, DVDs and memory sticks about 18,000 “carefully sorted” images of abused, dead and mutilated infants, a court filing said.

Prosecutors said Shaw’s collection contained “such horrific content that even seasoned forensic examiners in the United Kingdom and the United States found it difficult to describe and categorize without frequent breaks,” adding: “This is not rhetoric.”