A federal judge has refused to order busing to desegregate the St. Louis public schools on the ground that their racial imbalance is the result of housing patterns and not of deliberate government action.

Chief U.S. District Court Judge James H. Meredith found no constitutional violation in the racial makeup of the city's school. He said the imbalances that exist are the result of changing population patterns and not of school board policy.

"The cause for some remaining one-race or virtually one-race schools in St. Louis was the adoption of neighbourhood schools," he said. "There is no credible evidence that racially imbalanced schools were the result of gerrymandering, escapist transfers, or any other discriminatory acts."

The ruling came Thursday in a class-action suit brought against the State of Missouri by a group of black parents in February 1972. The parents later were joined by the Justice Department and the NAACP.

The suit charged the school board perpetuated racial segregation and discrimination "by its methods of maintaining and operating the school system." It said the board allocated funds in a discriminatory manner and ran "a dual biracial school system."

Meredith noted that a desegregation plan submitted by the NAACP calls for massive busing. "The court is of the opinion that such a plan is not feasible and would not be a stable plan of integration," he said.

Nearly 75 percent of the 73,000 pupils in the city system ar black.

Meredith found that 148 of the city's 181 elementary and high schools operating in 1973 enrolled 90 percent or more pupils of one race.

However, he said this resulted from the division of whites and blacks into two geographical areas of the city, and not from policies of the school board.

"A school system which assigns pupils to schools under the neighbourhood school policy will naturally be affected by this relationship," Meredith said.

"There is no credible evidence that the board deviated from the neighborhood school policy when necessary to prevent meaningful desegregation.

"As a matter of general principle, assigning school children to schools in their neighborhoods, does not offend the Constitution. Likewise, racial imbalance in schools is not in itself violative of the Constitution ..."

After hearing 13 weeks of testimony that ended last May, Meredith issued a 112-page ruling followed by a 27-page appednix.

Meredith ordered the board of education to submit within 90 days a plan "with such changes as the board deems appropriate under this decision" for further desegregating the schools.

"Since no constitutional violation has been found, the criteria shall be quality education, which includes integration of the races, where practical and feasible," he said.

Minnie Liddell, one of the parents who filed the suit, said Meredith's opinion "kicks us back a generation....We have not sweated all these years to end up with nothing. We'll scrape our pennies together and keep fighting." She vowed to appeal the decision to the Supreme Court if necessary.

School board members generally agreed that the dispute is not over. But Thomas . Teuth, one of the board's attorneys, said he was "delighted" by Meredith's ruling. "It's a good feeling when you win a case that will have tremendous impact on a community," he said.