United Food and Commercial Workers International Union, an organization that represents more than 1 million retail workers across the U.S., has come out with criticisms of Amazon’s $13.7 billion deal to buy Whole Foods Market, saying that the deal could hurt customers and workers and lead to significant automation of jobs.

In a letter to the Federal Trade Commission, UFCW President Marc Perrone called Amazon an “online retail monopoly” and argued that “the scope and weight of Amazon’s digital reach poses a severe and constant economic threat to consumers, retailers, and especially grocers, irrespective of whether they’re located online or are traditional brick-and-mortar stores.”

Amazon declined to comment.

Perrone claims that the deal will hurt consumers by reducing the number of grocery store choices and possibly impacting prices and food quality. He said he believes Amazon will automate jobs in stores by implementing something like the checkout-free technology being developed for Amazon Go stores.

Perrone in his letter does not call for the FTC to outright block the deal, but he asked the organization to “carefully review” the merger.

At the time of the announcement of the deal last month Amazon said it had no plans for layoffs or to automate Whole Foods stores using the technology it is developing for Amazon Go. Additionally, Brittain Ladd, a former manager at Amazon’s grocery arm AmazonFresh, recently told GeekWire he agrees that Amazon likely won’t implement the Amazon Go technology in Whole Foods Stores, at least not right away, because the stores are too large.

Though the deal sent grocery stocks spiraling when it was announced, Amazon and Whole Foods have a long way to go to catch the nation’s biggest grocer, Walmart. CNBC reported last month that Walmart has the highest marketshare in the grocery industry at 14.5 percent. Combined, Amazon and Whole Foods represent 1.4 percent of the grocery market.

Perrone and UFCW aren’t the only ones who have registered concerns about the Amazon Whole Foods deal in recent weeks. Multiple Congressional representatives have spoken on the deal.

Rep. David Cicilline, a Democrat from Rhode Island who sits on the House Judiciary Antitrust Subcommittee, has requested a hearing on the deal.

Following Amazon’s Prime Day, Rep. Cicilline Calls for Hearing on Acquisition of Whole Foods Market pic.twitter.com/vy7i5wUVPu — David Cicilline (@RepCicilline) July 13, 2017

Rep. Ro Khanna, a first-term Democrat who represents Silicon Valley, in an interview with The Atlantic called on federal officials to think differently about how they evaluate mergers. He wants to see the evaluation focus on a broader set of outcomes, such as wages, jobs and innovation.

Here is the full text of Perrone’s letter to the FTC: