The chief executive repeats his denial of claims he was spotted at a pro-democracy event in 1989 Donald Tsang Yam-kuen launched a robust defence of his integrity and dismissed as mo lei tau - which is Cantonese for nonsense - claims that he attended a pro-democracy concert in 1989. Denying for the second time in three days that he attended the Concert for Democracy in China, the chief executive said he cherished the people's trust in him throughout his long public service. 'Facts speak louder than words,' Mr Tsang said. 'I don't want to dwell on accusations which are groundless, unwarranted and mo lei tau. 'Let me say it once again. I have not participated in that event, and I mean, unequivocally, the Concert for Democracy in China.' The concert was held on May 27, 1989, in support of the ill-fated pro-democracy movement in Beijing's Tiananmen Square. Mr Tsang's integrity has been questioned after Szeto Wah, chairman of the Hong Kong Alliance in Support of Patriotic Democratic Movements in China, said the chief executive and his son had attended the concert at the Happy Valley racecourse 17 years ago. Mr Tsang, speaking through aides, said earlier this week that he had merely bumped into Mr Szeto after having dinner with his son at the Hong Kong Jockey Club - despite Mr Szeto recalling the encounter took place soon after 2pm. On Sunday, a man who worked as a volunteer at the concert was quoted by a Civic Party legislator as saying Mr Tsang spent about an hour at the event and that he recalled serving him some water. As the government's director of administration at the time, Mr Tsang would have broken civil service rules by attending the concert. Mr Tsang, who was speaking yesterday in Yunnan after a regional economic conference, said: 'It's almost 40 years since I joined the public service. I have always attached great importance to personal conduct and integrity.' He said the event was widely reported by the electronic and print media at that time, and, 'Any public figure or senior government officials participating could not have escaped the media attention and coverage.' Mr Szeto said Mr Tsang still needed to explain why he had taken his son to the racecourse where the event was held, adding, 'After all, he did not deny he and his son met us that day.' Ma Ngok, of the University of Science and Technology, said the controversy could become a political crisis if more concrete evidence against Mr Tsang were unearthed. He recalled the scandal which brought down financial secretary Antony Leung Kam-chung, who resigned in 2003 amid accusations he tried to cover up his purchase of a car shortly before he announced a rise in vehicle first-registration tax. 'The problem wasn't that serious to the public initially,' Mr Ma said. 'But once people get the impression that someone is telling lies to cover up, then it becomes fatal.' Li Pang-kwong, of Lingnan University, said the controversy might fade without strong evidence, such as pictures or video footage.