Civil rights enforcers are recommending that the city of Chicago be given 90 days to come up with a school desegregation plan or face the possibility of a federal lawsuit.

If filed, the suit would be the first by the Justice Department against a major northern district and the largest action yet. With 494,000 students, 78.5 percent of them from minority groups, Chicago's system has been under investigation for five years by the office of Cilvil Rights in the Department of Health, Education and Welfare.

The recommendation was contained in a letter drafted within the Office of Civil Rights for the signature of HEW Secretary Joseph A. Califano.A copy was obtained and published by the newsletter Education Daily.

It is "a staff-level draft which has not been approved " by Office of Civil Rights (OCR) DIRECTOR David Tatel, according to a spokesman for Tatel. Other HEW sources said the draft had not been formally forwarded to Califano either. Califano is responsible for asking the Department of Justice to take action against recalcitrant school districts once his Office of Civil Rights finds sufficient grounds.

The letter would inform Chicago superintendent of education Joseph P. Hannon that OCR had determined there was systemwide violation of the Civil Rights Act of 1964, "cereated, maintained and exacerbated" by "various policies and practices of Chicago school officials."

These policies, the draft says, involved the use of mobile classrooms rather than permanent ones; the redrawing of attendance area boundaries in some cases and the use of optional zones in others; dilscriminatory transfer, admission and faculty assignment practices; and the use of "segregative busing." Together, the policies "demonstrate the intent of school officials to segregate students by race", it says.

It would order Chicago to produce within 90 days a systemwide remedy for the situation. The remedy would include all schools and involve separate consideration of blacks and Hispanic students as well as Whites.The draft says it is "apparent" that any acceptable plan would involve busing.

Chicago school board spokesman Thomas Maloney said there was no way officials could respond to an unsigned draft. "This is an internal communication only," he said. "We are in close dialogue with HEW and I have no doubt that if there were going to be any communication [of this nature] it would have been shared with us in this dialogue rather than floated out in an unsigned letter."

The Illinois Board of Education has threatened to cut off state funds to Chicago unless a desegregation plan comes in before the end of March. Both state and OCR officials have found inadequate the voluntary compliance plan, called Access to Excellence, that Chicago launched with much fanfare last April.

Federal and state funding for Chicago education totals about $500 million, Maloney said.

He described the Access to Excellence plan as "a combination of education and desegregation. Quality education is THE priority and desegregation is A priority," he said. All the city's efforts had been developed in conjunction with citizen committee and fully discussed with OCR, whose director, Tatel, visited Chicago as recently as last week, Maloney said.

A recent status report on desegregation by the U.S. Commission on Civil Rights found the situation in Chicago "critical" and said the NAACP is actively considering legal action against the city.