A U.S. labor board has accused Amazon.com of unlawfully refusing to negotiate with a union that represents drivers working for a contractor, as announced by the agency on Wednesday.

The National Labor Relations Board (NLRB) has filed a complaint asserting that Amazon qualifies as a "joint employer" of the drivers employed by Battle Tested Strategies (BTS) and employed various illegal methods to deter union activities at a facility located in Palmdale, California.

Last year, BTS drivers voted to affiliate with the International Brotherhood of Teamsters union, marking them as the first Amazon delivery contractors to achieve union status.

In a complaint issued on Monday, the NLRB stated that Amazon violated the law by terminating its contract with BTS following the drivers' decision to unionize, without engaging in negotiations with the Teamsters first.

In August, the board indicated that it found merit in the union's allegations that Amazon exercises control over BTS drivers, thus should be recognized as their employer under federal labor regulations. At that time, the NLRB warned that it would file a complaint unless Amazon reached a settlement.

Additionally, the board announced last month its intention to file a second complaint concerning another group of Amazon drivers.

In response, Amazon spokesperson Eileen Hards stated that the NLRB's complaint did not encompass many of the Teamsters' allegations, suggesting that the union was "misrepresenting the facts."

"We have consistently maintained that there is no validity to any of their claims. We are eager to demonstrate this as the legal proceedings unfold and anticipate that the remaining allegations will also be dismissed," Hards remarked.

Amazon has previously asserted that it lacks sufficient control over the working conditions of drivers to be classified as their joint employer.

Teamsters President Sean O'Brien commented that Amazon is attempting to benefit from the labor of drivers while neglecting its responsibilities towards their welfare.

“This decision brings us one step closer to securing fair pay, improved working conditions, and appropriate contracts for Amazon workers," O'Brien stated.

Joint employment has emerged as a highly debated issue in U.S. labor relations over the past ten years, with the National Labor Relations Board's (NLRB) criteria for identifying joint employers undergoing multiple changes since the Obama administration.

Business organizations advocate for a standard that necessitates direct and immediate oversight of employees, whereas labor unions and Democratic lawmakers support a broader definition that includes indirect control.

An administrative judge in Los Angeles is set to hear the case, with an initial hearing scheduled for next March. The judge's ruling will be subject to review by the five-member NLRB, and any decisions made can be appealed in federal court.

If Amazon is determined to be a joint employer under federal labor regulations, this ruling could extend to other contractors associated with Amazon and compel the company to engage in negotiations with drivers' unions.

Additionally, the NLRB is contending with allegations from an increasing number of companies, including Amazon, asserting that its structure and internal enforcement processes are unconstitutional.

In a related development, Amazon has initiated legal action against the NLRB to prevent it from determining whether the company is obligated to negotiate with a union representing workers at a warehouse in New York City. A federal appeals court has temporarily halted the NLRB from making a ruling while it assesses Amazon's claims.