WASHINGTON (Reuters) -The top Democrat on the U.S. Senate Finance Committee accused the Trump administration of having inadequate customs procedures in place as it ended the "de minimis" U.S. tariff exemption for packages valued below $800, leading to severe disruptions in mail shipments to U.S. shoppers and small businesses.

Senator Ron Wyden in a letter to Commerce Secretary Howard Lutnick seen by Reuters requested answers on how the department concluded that adequate systems were in place to collect duties on low-value packages as the exemption ended on August 29.

Wyden, one of the Democratic Party's most influential voices on tax and trade matters in Congress, sought to put a negative spin on the administration's claim that it closed a dangerous trade loophole.

The de minimis exemption allowed nearly 1.4 billion packages to enter the U.S. duty free in 2024 and fueled a boom in direct-to-consumer e-commerce shipments from Chinese e-commerce firms Shein and Temu .

Wyden said the change was "hasty," leading to "mass disruptions in international shipments, confusion and increased costs for American consumers and small businesses." He cited data from the U.N.'s Universal Postal Union (UPU) showing that on August 29, the day the de minimis exemption ended, total postal shipments to the U.S. had fallen 81%.

"I have serious concerns about your judgment and seek additional information regarding your role in the decision to abruptly end de minimis without proper systems in place to handle the change," Wyden wrote in the letter to Lutnick.

The U.S. Customs and Border Protection agency, which is charged with collecting import duties, did not immediately respond to a request for comment, nor did the Commerce Department.

A spokesperson for the UPU said the agency would be updating its U.S. shipment figures, which do not include commercial express shipments such as those from FedEx or United Parcel Service, in coming weeks. The U.S. Postal Service declined to comment on incoming shipment volumes for foreign postal packages.

Shippers of illicit drugs and fentanyl precursor chemicals also have exploited de minimis due to limited inspections for many packages claiming the exemption.