He had engaged in sex with a 15-year-old after making the teen send him pictures of his genitals.
Renshaw made another boy, between the ages of 13 and 14, take a photo of his buttocks and send it to him after they engaged in 'touching of a sexual nature".
He was convicted of grooming the boys in June last year at Preston Crown Court before he went on trial at the Old Bailey for plotting to kill Ms Cooper and DC Henderson.
Renshaw, of Skelmersdale, Lancashire, twice stood trial for belonging to far right group National Action, along with 34-year-old Andrew Clarke, Latham Close, Trubini, of Dutton Court, Warrington, Cheshire, and Michal Trubini, 36.
But on Tuesday, a second Old Bailey jury failed to reach a verdict on the membership charge against them after deliberating for 48 hours and 13 minutes at the end of a month-long retrial.
The prosecution announced there would be no third trial.
National Action leader Christopher Lythgoe, 33, and Matthew Hankinson, 25, were convicted of membership of the proscribed organisation after the ban at the first trial in July last year.
Lythgoe was jailed for eight years and Hankinson for six.
Renshaw had admitted engaging in conduct in preparation for a terrorist act and making threats to kill.
Mrs Justice McGowan remanded Renshaw in custody ahead of sentence on a date to be fixed.
Renshaw was arrested on January 11, 2017 for stirring up racial hatred in relation to two speeches he made. As part of the investigation, his phone was examined.
DC Henderson discovered evidence of Renshaw's relationships with the underage boys and arrested him again on May 19.
Renshaw had told DC Henderson in interview that she was fabricating evidence for "the two worst things anyone could be - a homosexual and a paedophile".
He was released on bail and began researching DC Henderson to prepare for the revenge attack.
The paedophile was so determined to stop the detective revealing his paedophilia that he plotted to kill his local MP in a pub, take hostages and lure in detective to silence her before killing himself through "suicide by cop".
He revealed his plan to Lythgoe, who gave Renshaw his "blessing" for him to murder Ms Cooper at the Friar Penketh on July, 2017.
Renshaw did not mention to his far right friends that he had been abusing 13-15-year-old boys.
He told the Old Bailey he spent just under a month planning to kill Ms Cooper to "send the state a message".
Renshaw, a former BNP youth organiser, denied he was going to carry out the murder on behalf of National Action, adding: "It was on behalf of myself."
Jurors heard a speech he delivered to the Yorkshire Forum for Nationalists in 2016 in which he said Hitler had "showed mercy to people who did not deserve mercy", adding: "You do not show the Jew mercy."
Fellow neo-Nazi Hankinson said "what about a synagogue?" when he heard Renshaw's plan, according to former National Front and National Action member Robbie Mullen.
The 25-year-old acted as a whistleblower after he overheard the plan to kill Ms Cooper and contacted the anti-racism campaign group Hope Not Hate.
Mullen said he told Renshaw it would be a "bad idea" to kill children, and Nazi paedophile Renshaw responded: "All Jews are the same, they're all vermin."
Clarke "was just sat back with a smile on his face, giggling", when he heard the plan, Mullen told the Old Bailey.
Renshaw had planned to make a "white jihad" video explaining his motives for the terror attack.
But he was arrested on July 5, 2017 after Mullen blew the whistle.
Renshaw was convicted of four counts of inciting a child to engage in sexual activity, between February 2016 and January 2017, and two counts of inciting racial hatred.
He was sentenced to a total of three years in 2018 and now faces an additional sentence for engaging in conduct in preparation for a terrorist act and making threats to kill.
National Action was declared a terror group by then-Home Secretary Amber Rudd in December 2016 following the group's support of the murder of MP Jo Cox.
When asked who National Action's enemies were, Mullen said: "Basically everyone... Jews, blacks, Asians, every non-white race."
Lythgoe sent a series of encrypted emails to his subordinates days before the ban came into effect, reassuring them the organisation would carry on as normal, merely "shedding an old skin for a new one".
Renshaw, Clarke and Trubini claimed National Action did not exist after the ban and they were merely like-minded friends who met up to train at the gym, discuss politics and get drunk.
Mullen was granted immunity from prosecution for being a member of the group in return for him giving evidence.
He carried on as a member despite the group's proscription in 2016 and contacted Hope Not Hate in April 2017 to "get out of the organisation," he said.
Mullen alerted Hope Not Hate of Renshaw's plan, who then relayed the message to Ms Cooper.
Prosecutor Duncan Atkinson said: "She was of the same party - Labour - as Jo Cox MP had been.
"She was therefore perceived to have the same support for immigration to this country that had been advanced as a reason for Jo Cox's death, and more especially for National Action's support for the actions of her murderer."
Renshaw had searched online during May 2017 for how to cut the jugular artery and how long it would take to die after suffering such a wound
Mr Atkinson asked Clarke why he downloaded National Action images from a far right website after the ban.
Clarke said: "I thought I would download it as memorabilia, to me it is artwork. I wanted it for my own personal use."
The prosecutor suggested the "artwork" was also propaganda but Clarke replied: "It was a period in my life where you had gone out and spoke, whether people had agreed or disagreed with it, there was an element of nostalgia."
Slovakian-born Trubini said he bought Mein Kampf but stopped reading it because he found it boring.
He said: "It was boring it did not grip me so I left it.
"The beginning, the first 40 or 50 pages he was just writing about rights of workers and that unions were not doing enough for them, which I don't disagree with.
"So it was not because I disagree, it was because it did not grip me."
