The father of a young man found critically injured lying on a road on the New South Wales mid north coast last month has made a passionate appeal for public help.

Matthew Mitchell, 30, has not recovered consciousness and remains in the intensive care unit of Sydney's Royal North Shore hospital after being found lying on Graham Drive at Sandy Beach, near Coffs Harbour, at 11:00pm on Saturday August 17th.

His father Peter Mitchell said his son has little chance of making a full recovery.

"If anyone knows anything at all please let the police know," he said.

"Not only for us but just to make sure that whoever did this can't do it to anyone else because I wouldn't wish this on my worst enemy.

"It's an absolute nightmare.

'I'd swap places with Matthew if I could but I can't and it's just horrible."

Peter Mitchell says it is not known if his son was bashed or hit by a car.

"I've never seen him in one fight ever, I've never seen Matthew drunk ever once," he said.

"He's just a really loving caring kid and he didn't deserve this."

Local crime manager Inspector Peter O'Reilly said Mr Mitchell is very badly injured.

"He's continuing to have bleeding on the brain," he said.

"So it's not likely that he will have a very good outcome should he even wake up at some point in the future.

"We established Strike Force Dartmoor to investigate how his injuries occurred.

"There are people out there who know what has happened to Matthew and we're asking them to come forward to assist us."

Anyone with information can contact Crime Stoppers on 1800 333 000.