Former Trump adviser and investment advisor Peter Lewis resigned Monday after an FTC probe into his company’s ties to a controversial $1.9 billion sale of sole-transaction advisory services.

Lewis was one of Trump’s most ardent allies during the 2016 election cycle and helped build the Trump campaign.

In June, the FTC filed a complaint alleging that Lewis’ company had violated federal law by offering a “no-questions-asked” sole-action advisory service, known as “Bluwaters.”

The company has denied the charges.

The FTC announced Monday that it is looking into Lewis’ actions after it received more than 1,200 complaints in the past 12 months related to the services.

The complaint alleges that the company engaged in deceptive practices by charging customers a “premium” rate that would be lower than the average for other services and by selling advisory services that were not actually part of a single investment or asset.

Lewis’ former company, Blue Water Advisors, was also accused of misleading investors about the services and was sued in court.

Bolton, Oklahoma-based Blue Water did not immediately respond to a request for comment.

BluWater’s business model, which was sold off to private equity firm Wackenhut Partners in February 2018, is similar to that of other sole-trader firms, according to The Hill.

The firm, which has been in business since 2011, offers investment and asset-management services for private equity, private-equity firms and hedge funds.

The company has a large market capitalization and a valuation of $1 billion, according forbes.