In a paper submitted to Legco, the Civil Service Bureau explained that some directorate positions require foresight, analytical and innovation ability, and political sensitivity more than professional ability.
The bureau said the new appointment mechanism, which will involve in-service or open recruitment, can apply to posts with succession difficulty and lack of competition.
But it stressed that a majority of directorate posts will still be filled by internal promotion in future.
The bureau added that it plans to use the new mechanism to hire the commissioner for innovation and technology, the government chief information officer, the deputy commissioner for efficiency and the commissioner for sports.
It noted that the mechanism was already used to hire the head of the civil service college and the director of information services in a pilot scheme.