Robert Thompson's harrowing revelation years after killing James Bulger as a 10-year-old.

Robert Thompson and Jon Venables shocked the world when they murdered toddler James Bulger in 1993.

Their horrendous crime was made more difficult to understand by the then-10-year-olds’ silence.

But now Thompson’s words are being heard publicly for the first time, in the form of comments made to a parole board being aired in a new British documentary. And what the convicted killer had to say is shocking all those who have been following the case for more than two decades.

According to The Mirror, the program James Bulger: The New Revelations include Thompson sharing his own view of the crime and its aftermath via his parole testimony in 2001.

The then-18-year-old said that while he regretted killing James, he couldn’t deny the positive impact it had on his own life and considered himself a “better person” because of it.

“I do feel aware I am now a better person and have had a better life and a better education than if I had not committed the murder,” he told the board, as heard in the documentary, which will air on British television’s Channel 5 today.

“There is obviously an irony to this but it is part of my remorseful feelings as well.”

He claimed that at the time of the murder he was “out of control” and spending time with people who were “committing crimes”.

“I was out of control because my life on the streets was better for me than my life at home – there was nothing for me at home.”

Thompson and Venables lured two-year-old James Bulger away from his mother and walked him out of a Liverpool shopping centre in February 1993.

They walked with the boy for several kilometres before torturing and killing him, leaving his body by nearby rail tracks.

Thompson said that this crime was carried out in silence.

"Jon Venables and I did not speak to each other at all, as I remember, during the attack," he said.

"And we didn’t speak about it after we left James Bulger on the railway line."

The two boys were soon arrested and infamously treated as adults during the subsequent trial. Though both were found guilty, they had entered a not guilty plea.

At his parole hearing, Thompson explained why he was "unable to admit my part in the murder" - he feared revenge attacks.

"I wanted to tell what had happened, but I could not accept the blame, so I had to tell and put the blame for everything on Jon Venables’ shoulders."

"I was too frightened to accept any blame myself."

He also added: "I didn’t feel able to give evidence."

However, his statements still suggest that he viewed Venables as the lead killer.

“Looking back, I very much regret that I did nothing to stop it at the time and the sight of those photographs fills me with shame and revulsion."

But he did say that he understands the devastation he caused.

"I, personally, wish Mr and Mrs Bulger and their families to know that I am desperately sorry for what I did, and aware of the enormity of what I did," Thompson said.

"I am deeply ashamed of what I did, of having played a part in this horrible murder."

The testimony convinced the board to set him free. Along with Venables, he was released on lifelong parole, given a new identity to live out his life.

Unlike Venables - who spent three years in jail for breaching his parole in 2010 and is currently behind bars for possessing child abuse material - Thompson has had no known further convictions.

The documentary will speak to several people close to the case and promises to share "new and startling" revelations about the crime.

It is not yet known where the documentary, James Bulger: The New Revelations, will air in Australia.