Awwal 18, 1432 H / April 22, 2011, SPA -- Hong Kong journalists on Friday called on the government to uphold press freedom after an advertising company representing the city's commuter rail operator threatened to withdraw bookings if newspapers ran negative stories, according to dpa. The Hong Kong Journalists Association claimed the company called OMD wrote to several Chinese-language papers threatening to withdraw advertisements for its client the Mass Transit Rail Corporation Ltd (MTR) unless they comply. It also asked that the message be circulated among editors and journalists. The letters were sent after one newspaper this month published a news story criticizing one of the rail operator's property developments alongside an advertisement for the commuter rail. The rail company, which is 76.8-per-cent owned by the government, later issued an apology saying it had never intended to interfere with the freedom of the press. "The corporation has completed an investigation into the matter in which OMD misinterpreted the corporation's intention in a letter issued to the media organisations," it said. MTR had simply requested that OMD improve the positioning of its advertisements in newspapers, the statement said. The company said it "has requested OMD to withdraw the letter and make appropriate clarifications." MTR runs the city's mass transit rail network and is also behind several property developments. Mak Yin-ting, chairwoman of the Hong Kong Journalists Association, said the advertising company's behaviour was unacceptable and warned it could have far-reaching implications if tolerated. "MTR is a public utility company," Mak said. "It is not just an ordinary commercial company and its biggest stakeholder is the government. "We all know the government has said it respects press freedom. If so, then as the biggest shareholder of the MTR, it should order the MTR to withdraw this guideline and state publicly and clearly that it respects press freedom and will not use money or commercial pressure to jeopardize press freedom." Hong Kong, which reverted from British to Chinese sovereignty in 1997, has a mini-constitution that guarantees freedom of the press. The MTR company was formed in 1975 by the government to set up the rail network. In 2000, the government sold off a 23.2-per-cent stake in an initial public offering when the company was listed on the stock exchange.