BEIJING, June 30  -- The Communist Party of China (CPC) on Monday underscored its disciplinary inspection reforms, just as four of the country's former high-ranking officials were expelled from the Party.

A meeting of the Political Bureau of the CPC Central Committee on Monday approved an implementation plan of these inspection reforms, according to a statement released after the meeting presided by the CPC Central Committee's general secretary, Xi Jinping.

No detail of the reform plan was included in the statement.

Monday's meeting came as China's anti-corruption drive reached a new crescendo as four former high-ranking officials were expelled from the CPC one day ahead of its 93rd anniversary.

Xu Caihou, former vice chairman of China's Central Military Commission, Jiang Jiemin, former head of the State-owned Assets Supervision and Administration Commission, Li Dongsheng, former Vice Minister of Public Security and Wang Yongchun, former vice general manager of the China National Petroleum Corporation, were expelled from the CPC, the Party's Central Committee announced.

Calling the CPC's disciplinary inspection reforms a vital component of China's ongoing campaign to deepen reforms, the statement called on officials at all levels to exercise self-discipline and preserve their moral integrity.

They should also take the lead in improving their work style, building a clean government and fighting corruption, it said, adding that secretaries of CPC committees should be the first persons responsible in these regards.

Those who derelict their duties and fail to improve the Party's work style and build a clean government will be held accountable, it added.

The statement also highlighted a dual leadership scheme designed to grant more power to discipline inspection agencies.

Under the scheme, local discipline inspection agencies must report to not only the CPC committees at the same level but also the inspection agencies of their superior level when investigating cases.

The statement called to strengthen the leadership of superior discipline inspection agencies over subordinate ones, adding that inspectors must also be sent to top-level Party and State organs.

Also approved at Monday's meeting was a document containing the CPC Central Committee's opinions on an overhaul of China's household registration system.

The statement called for an orderly urbanization and for good public services to be made accessible to all people living in cities.