Mubarak builds power base on favorable public opinion ...and vows to put muzzle on Egypt's corrupt 'fat cats'

Egyptian President Hosni Mubarak's harsh warnings about corruption are echoing through Cairo's crowded cafes and markets, as people gossip about the entourage of ''fat cats'' who prospered under Anwar Sadat's infitah or ''open door'' economic policy.

''I will not be lenient with anyone whatever his status may be,'' said President Mubarak. ''I will not have compassion even for my brother -- even for the closest of relatives. Egypt is not an estate for its ruler, elite, or their relatives to freely indulge in.''

Newspapers and magazines are feeding on the public's growing interest by devoting full pages to covering cases of infitah corruption with links to Mr. Sadat's inner circle.

One such case is that of Alexandria multimillionaire Rashad Osman, whose wealth soared with the introduction of Sadat's open door policy seven years ago. According to Osman's own account, he and a partner initially invested $1,300 in a wood importing company.

Last summer, before he was stripped of his parliamentary immunity to face charges ranging from illegal possession of state land to bribing officials, smuggling drugs and evading taxes, his wealth was estimated at $260 million.

Other members of Sadat's inner circle whose reputation has been questioned lately include:

* Mr. Sadat's wife, Jihan, who was asked to present financial statements during the period of her husband's rule. Well-informed sources said she resisted at first, but later bowed to pressure. She was charged with receiving checks in her name for donations made to charity projects she supervised. The former director of the Nasser Bank was questioned recently about a tourist transportation system officially sponsored by the bank, but invested in by Mrs. Sadat.

* Mr. Sadat's brother-in-law and contracting tycoon, Osman Ahmed Osman, who undertook all major construction projects in Egypt during the Sadat era. As a result of recent investigations into his business dealings, half of his companies' subsidiary operations were suspended. One of these companies illegally had taken possession of state land worth $10.3 million.

* Mr. Sadat's younger brother, Talaat Sadat, was among a group of food importers blacklisted for having imported and marketed products inappropriate for human consumption.

* Another of Mr. Sadat's in-laws and one-time parliament speaker, Sayed Marei , has evaded paying $1.3 million in taxes over several years. The descendant of a rich landowning family, Mr. Marei owns a vast estate where select horses are bred for export.

So far, President Mubarak has moved swiftly to tighten government control over private business, and has issued directives to widen the scope and jurisdiction of specialized watchdog organizations dissolved under Mr. Sadat.

Meanwhile new names of top officials are being added to the list of infitah ''fat cats.'' The list already includes deputy prime minister for the economy under Sadat, Abdul Razzak Abdul Meguid, and minister of state for parliamentary affairs, Helmi Abdul Akher, both dropped in a recent Cabinet shakeup.