The Consumer Federation of America and the National Treasury Employes Union yesterday accused the federal government of dismantling its only independent check on oil imports information supplied by the petroleum industry

In a suit filed in federal court here, the two groups are seeking suspension, pending public comment, of a U.S. Customs Service plan to phase out monitoring of all petroleum and petroleum products imports as they inter the U.S..

On June 12, the Customs Service ordered its agents to stop checking all incoming petroleum shipments and instead to begin spot-checking about 5 percent of them.

The Customs checking program -- which the CFA claims revealed that the U.S. is receiving 10 percent more imported oil than acknowledged by the Department of Energy -- was the only one of 15 different sources tapped by the U.S. for oil import imformation that doesn't originate from data supplied by the petroleum industry.

"As consumer frustration with the administration is abandoning one of the few vehicles it had to double-check the accuracy of the figures which domestic oil commpanies furnish DOE," said Kathleen O'Reilly of the CFA, a federation of 240 consumer organizations from around the country.

O'Reilly also said the Custom Service decision "was made without notice to the consuming public in violation of the Administrative Procedures Act," thus providing the basis for the legal action.

Customs agents had boarded tankers to measure oil in order to determine the duty that would have to be paid on the shipment.

But the Carter administration's decision to lift price controls on the oil industry also ended petroleum import duties, thus eliminating the need to confirm the exact amount of oil being imported on any single shipment.