An arbitration panel has awarded a former broker at Allegiant Securities LLC $100,000 in a case that arbitrators said involved a forged letter purporting to be from the Financial Industry Regulatory Authority Inc.

Allegiant withheld commissions from Jay Weinstein, a broker at the firm, “based on a fraudulent claim that there was a Finra fine that had been levied against the firm,” said Brian Buckstein, the attorney who represented Mr. Weinstein.

A three-person Finra panel ruled recently that the president of Allegiant, “or someone under his direction or control, concocted a forged letter from Finra claiming that [Mr. Weinstein] was the subject of an ongoing investigation, which was false.”

In addition to the $100,000 award, which was formally issued late last month, Allegiant was ordered to pay Mr. Weinstein $57,500 in attorney’s fees and costs.

“We don’t know to this day who created” the phony letter, Mr. Buckstein said. “It’s the craziest document I’ve ever seen — it looks identical to a standard [investigatory] letter from Finra.”

Allegiant’s president, Dennis Flanagan, said he will attempt to have the award vacated.

We had nothing to do with” the forged Finra letter, he said.

“I had a contract” with Mr. Weinstein, Mr. Flanagan said. “I didn’t need a fake letter” to get paid the $11,000 Mr. Weinstein allegedly owed the firm.

The award was a “devastating blow to small firm like us that has never been in trouble,” he added.

A spokesman for Finra was not immediately available for comment.

The case began when Allegiant sued Mr. Weinstein for the money.

Mr. Weinstein counterclaimed, alleging defamation on his U-5 termination form.

The arbitration panel ordered removal of the defamatory information on Mr. Weinstein’s U-5.

Mr. Weinstein, who left Allegiant in June 2008, has since founded his own advisory firm, Independent Fiduciary Consultants LLC in Seattle.

He declined to comment about the case.