The organisers of a failed unionisation drive at an Amazon warehouse in Alabama said on Monday it petitioned for a new vote, claiming the tech and e-commerce giant improperly interfered with the election.

The Retail, Wholesale and Department Store Union said it filed objections on Friday with the National Labour Relations Board, claiming that Amazon "created an atmosphere of confusion, coercion and/or fear of reprisals and thus interfered with the employees' freedom of choice," a union statement said. 

The bitterly contested mail-in vote to unionise was rejected by a two-to-one margin according to the tally earlier this month, a stinging defeat in the push to create the first labor union at a US-based Amazon facility.

The results capped a bruising months-long battle that has sparked intense debate over workplace conditions at Amazon, which has more than 800,000 US employees.

The RWDSU said it filed 23 objections ranging from the placement of a collection box outside the facility which could allow the company to monitor voting, threatening lay-offs or loss of benefits, intimidation and other improper actions.

Amazon, which has repeatedly denied any impropriety, disputed the union's claims at the facility known as BHM1.

"The fact is that less than 16 per cent of employees at BHM1 voted to join a union," the company said.

"Rather than accepting these employees' choice, the union seems determined to continue misrepresenting the facts in order to drive its own agenda. We look forward to the next steps in the legal process."

The company has argued that most of its workers don't want or need a union and that it already provides more than most other employers, with a minimum $15 hourly wage and other benefits.

Amazon founder Jeff Bezos said last week that despite the vote, Amazon needs to do more for its employees.

"While the voting results were lopsided and our direct relationship with employees is strong, it's clear to me that we need a better vision for how we create value for employees — a vision for their success," he said in his annual letter to shareholders.