SEC Commissioner Michael Piwowar vowed to defend his agency's turf against the Financial Stability Oversight Council (FSOC), a panel of regulators created by the Dodd-Frank law to police emerging market risks. "With the council’s steady march, led by its self-appointed 'alpha dog' – the Fed – into areas that are solely within the SEC’s jurisdiction, I am concerned that our mission to protect investors, maintain fair, orderly, and efficient markets, and promote capital formation is being compromised," Piwowar said in a speech before the conservative-leaning American Enterprise Institute.

The FSOC is a council of regulators chaired by Treasury Secretary Jack Lew and made up of the heads of all the major regulators, including Fed Chair Janet Yellen and SEC Chair Mary Jo White.

Piwowar is not a member of the FSOC by law. He has repeatedly complained that he has been denied access to closed door FSOC meetings, even though other Federal Reserve officials who are also not FSOC members such as Fed Governor Daniel Tarullo have been able to attend.

A Treasury spokeswoman previously said the council defers to each member on who gets to come to top-level, closed-door meetings. FSOC members typically bring one staffer, but can bring more if requested.

Piwowar on Tuesday came up with several choice nicknames for the FSOC in his speech, including "The Firing Squad on Capitalism," "The Vast Left Wing Conspiracy To Hinder Capital Formation" and the "Unaccountable Capital Markets Death Panel."

"I am resolved to defend our jurisdiction," he added.

Spokeswomen for the Treasury and Fed declined to comment on his remarks, but in June testimony before a U.S. House of Representatives panel, Lew defended the work of the FSOC and bashed critics who raised questions about its activities.

"If we avoid or are discouraged from asking questions altogether, our financial system will be more exposed to unseen risks," he said.

He also said that people who claim the panel's operations are opaque are "simply wrong."

Piwowar has always been critical of the Fed and the FSOC. But his latest comments were arguably his strongest to date as discontent between the Fed and some SEC officials has grown in recent years.

Historically, the Federal Reserve and the SEC have always had some tension because of very different approaches to regulation.

That tension has grown since the passage of Dodd-Frank and the creation of the FSOC, a move that gave the Fed a greater role in systemic risk regulation.

The FSOC has the power to designate large financial firms as systemic, a tag that imposes more regulation and oversight by the Fed.

It has already used the new power to designate large financial companies, including American International Group Inc, GE Capital and Prudential Financial Inc.

The council has ruffled feathers among some SEC commissioners because of its governance structure, and because it has been eyeing areas that fall under the SEC's jurisdiction.

It is currently weighing whether the activities of large asset managers, which are regulated by the SEC, also pose risks to financial stability. It sought to pressure the SEC to adopt reforms for money market funds. And in prior written reports, the FSOC has cited other areas in the financial system that could pose risks, such as securities lending by brokerages and high-frequency traders.

Piwowar is not alone at the SEC in his views about FSOC. Two of his fellow commissioners have expressed concerns, saying they feel the agency's opinions are shut out on crucial policy matters and that the Fed has outsized influence.

Critics, including Piwowar, have also said the council lacks transparency in how it makes decisions about designations.

(Reporting by Sarah N. Lynch; Editing by Tom Brown and Andre Grenon)

By Sarah N. Lynch