A new Giuliani administration policy giving public housing applicants with the highest incomes first crack at vacant apartments has been blocked by a lawsuit charging it discriminates against poor blacks and Latinos.

The request for a temporary injunction filed in federal court last week by the Legal Aid Society isn’t due to be heard until mid-December, but it has already forced the New York City Housing Authority to delay its “income mixing” plan, slated to go on line before the end of the year. “We’re holding off on putting it into effect until the lawsuit is resolved,” said Authority spokeswoman Ruth Colon.

The proposed plan, which was approved by the federal Department of Housing and Urban Development this summer, gives top priority for public housing to working families with incomes between $24,000 and $49,000 a year. Extremely poor families who make up the majority of the quarter-million-name waiting list will be pushed to the bottom. Federal mandates requiring the city to house 1,400 homeless families in developments would still be in effect.

“The city is saying we will give priority to the least needy at the expense of the people who most need permanent shelter,” said Legal Aid litigation director, Scott Rosenberg.

Rosenberg charged that the policy will greatly increase the number of white tenants in the system and encourage their segregation in a few projects. According to analysis by the Philadelphia-based Center for Forensic Economic Studies, the number of new white tenants would double from about 300 tenants a year to 600, out of a total of about 6,000 move-ins. Coupled with NYCHA rules giving new residents more choice about which projects they move into, the plaintiffs allege the income-mixing scheme creates segregation in violation of the federal Fair Housing Act.

NYCHA officials denied the new policy has racial implications and said income-mixing is intended only to provide stability to the many city projects occupied primarily by poor families. NYCHA chairman Ruben Franco has also said the policy is necessary to increase rent revenues at a time when federal housing subsidies are diminishing.