(Bloomberg)—A federal judge, who is deciding whether to grant an injunction to halt the pending merger of Staples Inc. and Office Depot, criticized the U.S. Federal Trade Commission for attempting to elicit false information from an executive of Amazon.com Inc.

U.S. District Judge Emmet Sullivan in Washington said Wednesday it’s “very disturbing” when the U.S. tries to persuade a witness “to say something for the benefit of the United States of America that is not true,” according to a transcript of the hearing.

Shares of Staples, No. 66 in the B2B E-Commerce 300, and Office Depot (No. 87) surged after the judge’s remarks. Staples shares jumped Thursday morning as much as 7.8% to $10.83 in New York, the best intraday performance since February 2015. Office Depot climbed as much as 13% to $7.16, also the biggest rally in more than a year.

Sullivan made the comments after Prentis Wilson, vice president of Amazon Business, a part of Amazon.com that sells office supplies and other business and industrial products to companies, testified in the trial over the $6.3 billion deal.

Sullivan said Wilson declined to make comments under oath regarding a written statement, according to the transcript, which didn’t specify what the comments concerned. The judge added that he wanted the matter, which arose in a closed-door session, made public. The FTC denied that it had sought a false testimony by Amazon.

Wilson was called to testify by the FTC, which sued Staples in December, about Amazon’s nascent business selling office supplies to corporations. Amazon’s entry into the office-supply market is central to the case because Staples and Office Depot claim Amazon will be a formidable competitor to an enlarged Staples. The agency says that the two companies dominate the market for sales to large corporate customers and the tie-up would lead to higher prices for corporate customers.

Tara Reinhart, a lawyer for the FTC, told Sullivan that the agency “certainly never asked” Wilson to say something “that wasn’t true.”

Responding to FTC questioning on Tuesday, Wilson said Amazon had secured only one contract from a company with more than $250 million in revenue. On Wednesday, in response to questions from a lawyer for Staples, Wilson said that overall, about 300,000 businesses had opened accounts with Amazon in the first 11 months of its Amazon Business service.

Wilson’s lawyer, William Monts of Hogan Lovells US LLP, didn’t immediately reply to an e-mailed request for comment on the in-court exchange. FTC spokeswoman Betsy Lordan and Craig Berman, an Amazon spokesman, declined to comment.

The case is Federal Trade Commission v. Staples Inc., 15-cv-2115, U.S. District Court, District of Columbia (Washington).