CHIEF Secretary Anson Chan Fang On-sang is set to unveil the most sweeping public review of the powers and accountability of the Independent Commission Against Corruption (ICAC) since its inception as Hong Kong's most powerful law enforcement body 20 years ago. Mrs Chan is expected to reveal plans in the Legislative Council tomorrow, sparked by public fears of post-1997 abuses and demands for greater openness in the wake of the Alex Tsui Ka-kit sacking last November. The review will cover all aspects of the ICAC's work, the laws governing it and the role of those empowered to keep watch on its activities. It will also examine recent extensions of its vetting of senior Civil Service appointments and its own internal investigations - both subjects raised by existing private ICAC watchdogs following the sacking of Mr Tsui. ICAC Commissioner Bertrand de Speville has continued to keep the reasons from being made public, using Section 8 (2) of the ICAC Ordinance. The review of powers to be announced by Mrs Chan will expand on a review already under way by chief ICAC watchdog, the Advisory Committee on Corruption. The independent review will not only look at the investigative teeth available to the ICAC, but also the future of its five watchdogs, headed by the Advisory Committee. The watchdogs - consisting of all Government House appointees - currently fulfil only an advisory role on information provided solely by the ICAC, with the Commissioner answerable in law only to the Governor. ''There is no way the committee could review itself and have any creditability, that is a big part of why the review is needed. It is clear the public have fears about the ICAC and 1997 and these must be addressed openly,'' a source close to the review said. ''The balance between accountability and an effective and efficient ICAC is going to be the key.'' The review is also expected to take in the appointment of the first post-1997 commissioner and how to institute more safeguards after the change of sovereignty, when Hong Kong loses the ultimate scrutiny of the British Parliament. Mrs Chan is expected to announce plans for the creation of a new body appointed by the Governor, Chris Patten. The council is set to debate a motion from Christine Loh Kung-wai and amended by Selina Chow Liang Shuk-yee urging the Government to set up a broad-based committee to carry out a full review of the ICAC's powers and accountability, taking into account changes in Hong Kong's ''social circumstances''. The Post understands the body, to sit for a limited length of time, will make a public report to the Governor. Mrs Chan was unavailable for comment yesterday but a spokesman for her said: ''ICAC's success is built on community support. Continued support is critical to the success of the fight against corruption.'' The spokesman added: ''Accepting that circumstances have changed considerably since the establishment of ICAC 20 years ago, the Commissioner himself has said publicly that it is now time to take another look at the ICAC's powers.'' Commissioner de Speville, currently preparing papers for the Advisory Committee's probe, said last night it was up to the administration to comment on the formation of any committee. He added: ''But as I said in my speech to AmCham [the American Chamber of Commerce] last week, 20 years on seems to be a good time to look again at the powers of the commission.'' At the time he said: ''. . . it seems to me that our system of accountability, extensive though it is, merits examination to see if it can be improved upon. ''The commission has got very wide powers and I for one believe that the legislature and the administration should review those powers from time to time.'' However, Mr de Speville also warned that there was a point at which ''accountability ceases to become a virtue''. ''Some information has to remain confidential to protect reputations or to avoid compromising investigations - it is not in the public interest that such information should be public information.''