Leung also came under fire for appointing Kao – a staunch supporter – to advise the administration on appointments to other advisory bodies, which was said to have enabled cronyism.

The two other full-time advisers leaving their posts are Lee Tak-keung and Wong Chack-kie.

The unit is currently largely advisory and in charge of research on public policy and also drafts the chief executive’s annual policy address.

It is understood that an administrative officer will be appointed to head a review of the unit’s operations, which is expected to be completed in a few months’ time.

The future unit is also expected to co-ordinate bureaus in the formulation of policies while the chief secretary’s office looks after policy implementation.

But Lau Siu-kai, former head of the unit, warned on Wednesday that the overhaul might create more political tension and that the government should have clear guidelines on its job responsibilities to avoid “too much competition” between the unit and other departments.

“In the past, the CPU rarely touched on any actual daily administrative management, but if it needs to be more hands on in helping with coordination, then the unit will likely have to be more involved in participating in the government’s daily operational work than before,” Lau said on an RTHK programme.

“In this process, government officials are likely to be quite resistant to this change.”