A private, non-profit task force, saying homelessness is only "the most visible" U.S. housing problem, called Monday for a 12-year housing program to provide "fit, livable and affordable housing by the year 2000."

Sens. Alan Cranston, D-Calif., and Alphonse D'Amato, R-N.Y., who requested the study and began a major congressional study of the nation's neglected housing programs, promised to speed up major housing reforms in Congress."Each passing month brings clearer evidence of a growing housing crisis," Cranston told a news conference called to release the 88-page report. He promised to have a reform bill introduced in the House and Senate in July and before the full Senate by the Aug. 15 recess.

The new report, expected to provide the centerpiece of the legislation, was prepared by the private, 26-member National Housing Task Force headed by one of the nation's most prominent developers, James Rouse, and David O. Maxwell, chairman of the board of Fannie Mae, the Federal National Mortgage Association.

At the heart of the report was a call to reverse the Reagan administration's hands-off policy toward housing especially for the poor by committing $3.4 billion a year over 12 years in an effort to ease both the homeownership crisis and the need for low-income housing.

"The federal government must re-establish its historic role as a full partner in the effort to revitalize housing," the report said in presenting the 10-point reform program.

While noting that the country has made great progress in providing housing for most Americans, it also said, "In the midst of this manifest success is a growing horror story of which the problem of homelessness is the most visible."

D'Amato, citing the report's statistics on the decline of home ownership rates, particularly among the young, said that the nation's housing crisis "no longer affects only the homeless and the poor. It has spread to young working families who see home prices skyrocketing at a time when they cannot save a downpayment because of ever-increasing rent, student loan debts and static incomes."

The report said the nation's homeownership rate has slipped from 65.6 percent to 63.6 percent, reversing a 40-year trend of increased ownership. The figures mean nearly 2 million fewer families now own homes.

"The housing problems of the poor, however, are beyond solution by the market system alone and have fallen outside the focused attention of our society," the report said. "Many of the poor are unseen or unnoticed by the majority of Americans. ... But none of us can fail to be moved by the sight of the homeless, whose growing presence in our streets is a daily reminder of their plight."

It noted that the number of non-subsidized, low-income renter households has grown from 3.8 million in 1974 to 4.5 million in 1987.