Exiled mainland dissident Wang Dan defended the role of fellow student leader Chai Ling in the 1989 Tiananmen protest, as he wrote for the second time to Hong Kong university students ahead of the 20th anniversary of the bloody crackdown. In an open letter to student union members at the University of Hong Kong after they passed a motion about the 1989 democratic movement, Dr Wang said: 'I would like to thank HKU students. You have passed a referendum with an overwhelming majority to demand the vindication of June 4, which has cleaned HKU students' reputation and has proved again that the pursuance of democracy is a basic human principle.' Union president Ayo Chan Yi-ngok had criticised Ms Chai as a 'runaway student leader'. He also said military suppression could have been avoided had demonstrators dispersed peacefully. His views on the June 4 incident sparked controversy, and this week students will vote on a motion to dismiss him from his position. In a vote last week to support a motion calling on Beijing to vindicate the 1989 democratic movement and be held accountable for the June 4 crackdown, 92.6 per cent of the valid votes were in favour. Dr Wang said Mr Chan's remarks were an example among 'a lot of unfair comments on Chai Ling'. 'Some people are even more acrimonious to Chai Ling than to the slaughterers. Is there still justice in this world?' he said. Dr Wang, a scholar who lives in Los Angeles, said he had not contacted Ms Chai for four or five years. He added that although she had not been active in the democracy movement in recent years, Mr Ayo's allegation against her was not fair. Ms Chai is now president of an internet company in the US city of Boston, Massachusetts. Dr Wang's letter was published in the Chinese-language Ming Pao yesterday. It was the second time he had written to local young people since the HKU controversy began. He has been invited by the Hong Kong Alliance in Support of Patriotic Democratic Movements in China to attend Tiananmen commemorations but the government has not indicated whether he will be allowed to enter the city or not. Dr Wang has failed to obtain a Chinese visa since his expired in 2003 and his application for a Hong Kong visa was rejected last year. Another guest invited by the alliance, Danish sculptor and human rights activist Jens Galschiot, wrote to the Immigration Department on Friday applying for entry. He was denied entry to Hong Kong during the Olympic torch relay last year. 'It is my clear understanding that there [were] political reasons behind refusing me entrance into Hong Kong last year,' he wrote. 'I find it important that the treatment of a case like this is carried out with full openness and transparency.' During the trip he plans to repair the Pillar of Shame sculpture at HKU, which he made in 1997 in memory of the Tiananmen crackdown, and attend ceremonies related to its 20th anniversary. He also told the department he would like to visit his two sons, as well as two film crews, which planned to shoot a documentary. A department spokesman would not comment.