Coinbase's former top legal adviser sold over $4 million in stock options when he left to take the helm at the U.S government's banking supervisor.

Brian Brooks, who was the cryptocurrency exchange's chief legal officer from late 2018 until last month, sold his stock options to become interim head at the Office of the Comptroller of the Currency (OCC) – a 3,600-person bureau in the U.S. Treasury Department.

Financial disclosures seen by Bloomberg show Brooks sold $4.6 million stock options in Coinbase, earned on top of a $1.4 million salary, to take up his new role as acting comptroller – a position that earns less than $300,000 a year.

Brooks had joined the OCC back in March as chief operating officer and first deputy controller, but assumed the position of acting comptroller following the sudden departure of his predecessor, Joseph Otting, halfway through a five-year term, in May.

Brooks was confirmed as acting comptroller on May 29.

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The OCC's primary role is to maintain the integrity of the U.S. banking system, encourage greater competition and innovation as well as ensuring full regulatory compliance.

In the past, the OCC has been accused of becoming too cozy with the financial institutions it is supposed to watch over. In late 2017, in his second week in the job, Otting scrapped longstanding plans to move hundreds of OCC staff out of the Manhattan offices of JPMorgan, Citigroup and other large-scale lenders. At the time, he said the move was "not practical."

In his inaugural statement, Brooks said he planned to foster innovation in the banking sector: "We should support banks’ use of new technology, products, and models that safely and fairly accelerate the velocity of money, create greater financial inclusion, and empower consumers and businesses with more control over their financial affairs."

See also: US Bank Regulator OCC Asks for Public Input on Cryptocurrency Use in Financial Sector

In an interview with CoinDesk, Brooks went further: “My job here is not to protect incumbents, and it’s not to preserve the status quo...The job I have is to make sure that the bank charter’s flexible enough to maintain a safe, sound, strong American economy and the shape of banking has to be flexible to accommodate.”

As he is only acting comptroller, Brooks doesn't yet face the same ethics restrictions he would if he led the regulator permanently. Still, he has assured the OCC's ethics department he will stay away from any investments that could present any conflict of interest, which include tech firms such as Amazon and Coinbase.

See also: Capitol Controls: From Coinbase to the OCC, How Brian Brooks Is Changing Regulation

In a letter, Sunday, U.S. senator and former presidential candidate Elizabeth Warren urged Brooks to undo some of the actions from the previous OCC administration which, she said, had been "tainted by Comptroller Otting’s own conflicts of interest."