LONDON, Oct 29 (Reuters) - Two men who ran Scotland's biggest known paedophile ring were jailed for life on Thursday for a string of child abuse offences, including the sexual assault of a three-month-old baby.

Neil Strachan, 41, was found guilty earlier this year of trying to rape an 18-month-old boy and sexually assaulting a six-year-old boy and James Rennie, 38, was convicted of molesting a young boy for more than four years.

That abuse started when the child was just three months old. "Today represents the conclusion of the trial of the most prolific child abuse network ever identified in Scotland," said Detective Superintendent Allan Jones of Lothian and Borders Police.

"Any reasonable human being would be repulsed by these men's vile acts, the images they shared, and the discussions they participated in online."

Strachan, who is HIV-positive and a convicted sex offender, was ordered to spend a minimum of 16 years behind bars, at the High Court in Edinburgh, the Press Association reported.

Rennie, once a prominent and respected gay youth worker, was told he must spend at least 13 years in jail.

The pair, both from Edinburgh, were also convicted of a string of child porn charges, alongside six other men who have already been sentenced. They were further found guilty of conspiring to abuse children.

The court was told Strachan abused the 18-month-old boy after being becoming a friend of the family and being entrusted with the child's care.

The abuse was captured in a photograph referred to as the "Hogmanay image".

"By its very nature, what is shown in that photograph is utterly appalling and would shock to the core any right-minded person who has had to see it," Judge Lord Bannatyne told him.

"Over and above that, this offence involves the most gross level of breach of trust. You breached that trust in the way shown in the 'Hogmanay image' in order to satisfy your base sexual interests."

The judge said Rennie was at the heart of the conspiracy to abuse youngsters and likened him to a spider weaving an electronic web to bring about his crime.

The judge said Rennie, the ex-boss of LGBT Youth Scotland, an organisation dedicated to helping young lesbian, gay, bisexual and transgender people, had also betrayed the parents of his victim to a "truly appalling" extent.

Strachan, who had two previous convictions for lewd and libidinous practices with young children, was found to have 7,223 still pictures of abuse and 184 video images, while Rennie had 6,545 photographs and 662 movie files.

"No jail sentence, however lengthy, will ever begin to compensate Strachan and Rennie's victims," Jones said.