A coalition of farm worker organizations has accused the Carter administration of discriminating against farm workers in enforcement of labor laws and has won its first round in court.

The group is charging that the Labor Department, under Secretary Ray Marshall, a longtime advocate of migrant workers' rights, has failed to live up to a 1973 court order mandating a broad range of services for migrant and seasonal farm workers.

The original order, which found the department to be discriminating against farm workers by failing to deliver services authorized by Congress and required sweeping corrective action, was aimed at the Nixon administration.

The new complaint filed on behalf of about 70 local and regional farm worker organizations alleges there is still a "concerted strategy of delay, diversion and broken promises" on the part of the Labor Department bureaucracy, continuing into the present administration.

After several months of negotiations aimed at beefing up services for farm workers, the group - represented by attorneys from the Washington-based Arnold and Porter law firm - asked U.S. District Court Judge Charles R. Richey to order the department to demonstrate why it shouldn't be found in violation of the 1973 order.

Richey, who made the earlier finding of discrimination, not only ordered the department earlier this month to "show cause" why it is not violating the five-year-old mandate but interpreted the order more broadly than the department did.

The Labor Department contended that the order covered only employment services, while the farm worker groups argued it also covers wage-hour regulations, occupational safety and health regulations, and rules governing registration of labor crew leaders. Richey agreed with the workers.

The Labor Department is now in the process of responding to the order. Meanwhile, aides to Marshall say the department is doing all it can, considerig budgetary constraints and other priorities.

"We think we're doing as good a job as we can under the circumstances," said Charles Knapp, a special assistance to Marshall and former co-worker on academic matters dealing with farm labor problems, "but we can't satisfy all the constituent groups all the time. Nobody, but nobody, thinks they're getting enough."

Knapp noted that about $31 million of Comprehensive Employment and Training Act grant money has goneto farm workers, which he said represented a sizeable investment by the new administration.

Knapp conceded that Marshall has not been involved personally in the dispute, delegating the matter instead to under secretary Robert J. Brown. This is one of the farm worker group's main complaints. We've tried about every three months to meet with (Marshall) but his lawyers keep saying no," said Tom Jones, national representative of the National Association of Farmworker Organizations.

Richey, too, has suggested obliquely that Marshall take an iterest in the ease, asserting his respect for the secretary's experience in the field.

Jones notes with irony that farm labor research Marshall did while an economics professor at the University of Texas was used in the case against the Labor Department five years ago.

Among the remedies being sought by the farm worker organizations are: creation of an Office of Farmworker Protection within the department to oversee a more coordinated enforcement effort, expanded monitoring systems for compliance with worker protection laws, and new regulations to "minimize or eliminate the opportunity for discrimination."