Bernard Tomic's father says he will begin legal action against Davis Cup captain Lleyton Hewitt over an incident he alleges happened nine years ago.

The news follows the bitter war of words between Hewitt and Tomic that has raged all week at the Australian Open in Melbourne.

John Tomic told the Sydney Morning Herald that Hewitt left his son traumatised when he was 17 following an incident in 2010 during a Davis Cup tie when he tried to pressure him into revealing who in Tennis Australia was "against" him.

Bernard Tomic this week claimed none of the Australian players liked Hewitt with the two-time grand slam winner hitting back by accusing the Queenslander had threatened him and his family and tried to blackmail him.

"Bernard said something on the television before that Lleyton didn't like," Tomic snr said.

"[Hewitt] came into Bernard's room, closed the door and pushed [Davis Cup captain] John Fitzgerald out and he said, 'You have to tell me who from TA is against me'."

Australia's Bernard Tomic reacts after his defeat against Croatia's Marin Cilic during their men's singles match on day one of the Australian Open. DAVID GRAY/AFP/Getty Images

Tomic Snr said Hewitt was on crutches at the time and told his son he would not play Davis Cup for Australia again unless he spoke up about TA.

"He tried to force him to say something," Tomic Snr said.

"Bernard was shocked, he couldn't sleep all night.

"Bernard had made a comment at Melbourne Park that mentioned Lleyton Hewitt. That comment Lleyton didn't like and he asked, 'Who told you to say that?'

"He was young ... 16 and a half or 17. How can you come in the room and threaten him and say you won't play Davis Cup and say you won't be close to me if you don't tell me who from Tennis Australia is telling you what to say?"

He said they would take legal action against Hewitt next week.

"We will prove that Bernard has trauma from 2010 when Bernard was the youngest player in Davis Cup for Australia," he said.

"They will try to protect him but we will find the truth in the court."