(CNN)Matthew Whitaker, the acting US attorney general, was on the advisory board of a Florida company that was shut down by the Federal Trade Commission and served with a $26 million judgment earlier this year for what court documents called "a scam that has bilked thousands of consumers out of millions of dollars."

The company, World Patent Marketing, promised to help inventors get patents.

Whitaker was named as an advisory board member in October 2014 and Federal Election Commission filings showed the company's owner donated $2,600 to Whitaker's campaign when he was running for the US Senate. A payment record also shows Whitaker was paid at least $9,375 by the company from October 2014 to February 2016, and was due to be paid an additional $7,500 in 2016 and 2017, but it is unclear whether he received that money. ...

Whitaker was so involved in the company he sent a threatening email to a disgruntled customer, which was filed in the case by the FTC. In it, Whitaker accuses a customer of "blackmail or extortion" because the customer had threatened to complain to the Better Business Bureau.

"I am a former United States Attorney for the Southern District of Iowa," the email says. "I am assuming you understand that there could be serious civil and criminal consequences for you" if the customer filed a complaint, Whitaker wrote, adding, "Understand that we take threats like this quite seriously."

The customer responded that Whitaker was "party (to) a scam."

Whitaker, through the Justice Department, declined to comment.