A convicted knifeman who is on the run in Sussex spoke out against the regime of his young offender institution.

Ross Macpherson – a criminal rated at the highest risk level by Sussex Police – was reported missing on Wednesday and was still on the run last night.

As police searched the county for the 22-year-old, it emerged he had written a letter in a prisoners’ newspaper condemning the tactics of prison staff. Macpherson went missing from Surrey within weeks of being released on licence last month.

Police warned he could be armed with a knife. Yesterday they were searching for him at addresses of known friends and they carried out at least one raid in Worthing, but he remained at large.

Macpherson was jailed in 2006 for causing grievous bodily harm by stabbing a 17-year-old in the stomach. While still in custody, Macpherson wrote a letter to Inside Times criticising restraint techniques, including “nose distraction”, used on youths.

He said the controversial method “does nothing but give staff the right to stick a finger up each nostril, pull your nose back and punch you in the face while six fully grown men pin you down”.

The piece is reproduced on a page in his name on social networking website Facebook.

He wrote: “All it does... is reinforcing the lesson that power equals violence and brutality.

“And the same institution that teaches this lesson wonders why there is such a high level of youth knife crime.

“I’m not surprised these kids go on to join gangs and participate in acts of extreme violence and see no wrong doing.”

Macpherson is originally from Shoreham. Sussex Police said he had links to the town, as well as to Worthing and Guildford.

He is described as 5ft 10in, slim, athletic, with dark blue eyes.

He was last seen wearing dark jeans, a blue T-shirt and a dark jumper. Police said that under their “multi-agency public protection arrangements” – used to manage offenders living in the community – he was rated as one of the most dangerous vio- lent offenders.

Officers have warned the public not to approach him. Anyone who knows his whereabouts is asked to call Sussex Police on 101, quoting Operation Marshall, or serial 1923 of May 2.

Alternatively call Crimestoppers anonymously on 0800 555111.