A doctor who is suing his father has described the man as "nasty", comparing him to a loan shark. Testifying in High Court yesterday, Dr Lam Chuen-lung accused his father Lam Sing-yin, 72, of distributing defamatory posters near his clinic in Lam Tin and his children's schools in Mong Kok and Kowloon Tong. "How can a man be so nasty?" the son said. "How could he harass my children? He has failed as a grandfather." The doctor is suing his estranged father for putting up defamatory posters accusing him of cheating the elderly man of his money and properties. He is seeking at least HK$800,000 in compensation for serious damage to his reputation. The son told the court that his father once chased him in a car park, trying to hit him. After the son got into his car, the father hit the vehicle with an object and tried to stop him driving away. "On one occasion, I knelt down in my clinic, pleading with my father to stop disturbing me." The doctor also said he once borrowed HK$700,000 from the older man but was asked to repay HK$1.5 million. "It's worse than borrowing money from loan sharks," he said. The defamation suit is the latest twist in a long-running feud between the father and son. Between 2008 and 2009, the son called the police 12 times, accusing his parents of causing disturbances at his clinic. The father was given a suspended five-month jail sentence in 2010 over criminal intimidation for confronting his son with a knife at the clinic. The conviction was overturned on appeal. Later, the son sought to evict his parents from the flat they were living in at Sceneway Garden in Lam Tin and to sell it. That was followed by an application for an injunction to bar his father from getting near his clinic. The posters claimed the doctor had to repeat three years of education and did not complete his studies until he was 28 years old. He deceived his father into handing over money and shops, then framed him and hauled him to court, the posters claimed. The father told the court yesterday that his son still owed him more than HK$1.8million. The trial continues before Mr Justice David Lok Kai-hong.