Organized groups of squatters plan to take over federally owned vacant houses in seven cities today in an effort to pressure the administration to provide low-income housing.

Members of a welfare-rights activist group called ACORN already have barged into more than 175 abandoned houses in 12 cities in the past few months and, with rallies and fanfare, have taken possession of city-owned properties.

The group is demanding that the Department of Housing and Urban Development turn its vacant properties over to families that are willing to fix them up.

The seven cities are Detroit; St. Louis; Dallas; Phoenix; Fort Worth; Lansing, Mich.; and Columbus, Ohio. A spokeswoman for ACORN -- Association of Community Organizations for Reform Now -- said about 20 families in all will move into vacant HUD-owned houses, acquired through foreclosures on FHA-insured properties.

Madeleine Adamson, an ACORN representative in Washington, said that HUD has about 10,000 empty homes across the country that could be used by low-income families.

HUD Secretary Samuel R. Pierce Jr. said the squatters would not be tolerated.

"They have no title or lease and therefore no legal right to occupy the property. Accordingly, they will be removed," Pierce said through a spokesman. "If we were to treat squatters or squatter-rights groups as having legitimate rights to property, we would in essence be encouraging the continuation and expansion of this type of activity, undermining our property disposition efforts."

HUD properties acquired through foreclosure usually are sold at auction.

ACORN also has charged that HUD has been too quick to allow foreclosure on delinquent FHA mortgages and is calling for an end to all foreclosures due to unemployment or illness or other circumstances beyond the homeowner's control.

Later this month, ACORN plans to set up a three-day tent city in Washington.