After months of charges that he was waffling on the matter, Mayor Art Agnos has ordered the police to break up a sprawling encampment of homeless people just outside City Hall.

The Mayor's order, issued last week and made public Tuesday, has been denounced by advocates for the homeless, who contend that a new city program intended as an alternative to the encampment will only break up homeless couples and force many people into jails, doorways or alleys.

Mr. Agnos's order will take effect Friday. It directs the police to begin enforcing laws long on the books that bar sleeping in public places, and it signals the end of his tolerance for what critics have come to call ''Camp Agnos.''

For years, as many as 350 homeless people at a time have occupied the camp, situated along the one-block-square Civic Center plaza. The homeless have been drawn there by the shade of the plaza's trees, its flat landscaping and the fact that until now they have not faced arrest.