A White House public relations technique that helps US President George W. Bush sell his message was used at a Hong Kong government media conference yesterday to announce the national security bill. Slogans such as 'Freedom in Research', 'Freedom of Association' and 'Freedom of Speech' appeared on a sky-blue backdrop to ensure clear delivery of the message, a method Mr Bush used last July when he announced new legislation on corporate governance. Political commentator Andy Ho said the strategy, which exploits the viewers' subconscious, was first used by former US president Ronald Reagan in the 1980s. Mr Ho said visual images stay in the mind for a long time and can change perceptions without the viewer realising it. 'The government must be exploring all possible communication channels to reinforce its message.' He also questioned the use of the tactic, saying 'it manipulates the public's subconscious . . . this is not ethical'. But Ma Ngok, assistant professor with the University of Science and Technology's social science division, said he did not believe the tactic would change the public's perception of the bill. Chief Executive Tung Chee-hwa used the same method last month when outlining changes to the security law proposals. A government spokeswoman denied it was copying the White House technique, saying 'it is a very common creative concept . . . we have used it in many previous functions.'