ATLANTA — Fed by antagonism toward President Obama, resentment toward changing racial demographics and the economic rift between rich and poor, the number of so-called hate groups and antigovernment organizations in the nation has continued to grow, according to a report released Wednesday by the Southern Poverty Law Center.

The center, which has kept track of such groups for 30 years, recorded 1,018 hate groups operating last year.

The number of groups whose ideology is organized against specific racial, religious, sexual or other characteristics has risen steadily since 2000, when 602 were identified, the center said. Antigay groups, for example, have risen to 27 from 17 in 2010.

The report also described a “stunning” rise in the number of groups it identifies as part of the so-called patriot and militia movements, whose ideologies include deep distrust of the federal government.