The Securities and Exchange Commission headquarters in Washington. (Anonymous/AP)

A federal investigation into Washington-style insider trading got the green light to continue this week when a judge ruled that congressional staff must provide information to investigators about possible leaks of sensitive information to investors.

The Securities and Exchange Commission launched the inquiry in 2014 after reports of a surge in health-care stock trading in the moments after a Washington-based brokerage provided its clients advance notice of a pending change in insurance regulations.

In his ruling, released this week but dated Nov. 13, U.S. District Judge Paul Gardephe said that the House Ways and Means Committee must respond to an SEC subpoena by providing information about any communications that might have been used by traders.

The investigation has focused attention on a relatively new and highly lucrative form of Washington consulting in which “political intelligence” firms leverage their connections on Capitol Hill and inside executive agencies to provide investors with special insights to inform their trading decisions.

That Washington-to-Wall Street communication is at the heart of the SEC investigation into the health-insurance stock surge. The episode began after a Washington-based firm, Height Securities, published an alert to clients on April 1, 2013, predicting an imminent change in a rule governing health insurance companies participating in a Medicare program.

The alert came about 20 minutes before the close of trading that day, triggering an immediate spike of trading of Humana, Aetna and other large health insurance firms. The rule change was announced publicly by the Department of Health and Human Services later that day — after the markets closed.

The Wall Street Journal and The Washington Post detailed trading spikes in Humana stock at the time investors were told about the likelihood of the regulatory change.

The investigation by the SEC is one of the first that followed the enactment in 2012 of the Stock Act, which forbids members of Congress or their staffs from trading on insider information.

In opposing the SEC’s subpoena, lawyers for the House cited protection provided to Congress by the speech and debate clause of the Constitution. Gardephe acknowledged the protection in his ruling but said it was limited. He wrote that while the committee did not have to turn over information directly related to “legislative activity,” it nevertheless must disclose information about communications with parties outside Congress.

Officials at the House Ways and Means Committee did not respond to requests for comment.

The SEC also issued subpoenas to the Greenberg Traurig law firm and a health-care lobbyist on its payroll at the time. Height Securities was then a Greenberg Traurig client. The law firm did not respond to requests for comment but has said that it was fully cooperating with the inquiry and had decided to no longer accept political-intelligence firms as clients.

Height Securities did not receive a subpoena, according to people familiar with the probe. The company did not respond to requests for comment.

An SEC spokesman referred reporters to the court decision.

Alice Crites contributed to this report.