Nearly half of the lobbyists who were registered with Congress in 2011 and then went “inactive” in 2012 remained with the same employer, and many continued to influence public policy, according to a study released Wednesday.

The finding by the nonpartisan Center for Responsive Politics illustrates a factor behind the recent decline in federally reported lobbying fees and the number of active lobbyists on K Street: Professionals are taking on roles that leave no public trail because their activities fall outside the scope of disclosure laws.

“Much of the decline in lobbying activity is not a decline at all, but rather the side effect of lobbyists and lobbying firms taking advantage of a feature of the law which allows them to continue influencing policy from ‘behind the scenes,’” the study concludes.

“By working as policy advisors and in other ‘non-lobbyist’ positions, former lobbyists can keep their current jobs but escape the consequences of being a registered lobbyist, leading people in and out of lobbying to suggest that those consequences act as a deterrent to transparency,” the study states.

The Lobbying Disclosure Act requires regular reports from individuals who make at least two lobbying contacts with covered government officials and who spend at least 20 percent of their time on lobbying activities for which they are paid. Grass-roots activism, most issue advertising and public relations work, even when part of an effort to persuade members of Congress, are exempt.

Several high-profile members of the advocacy business, such as former Sen. Tom Daschle, D-S.D., work on policy matters as “unlobbyists.”

The CRP focused on a subset of lobbyists who had been subject to the federal reporting requirements but then de-registered and stopped reporting their clients or estimated income.

The study examined 1,700 ex-lobbyists from 2011 to 2012 and found that 46 percent were still with their same employer and many had the same title or job description.

One lobbyist, Mark Smith of the Da Vinci Group, did not appear on 2012 filings but continued to describe himself on Twitter as a “proud lobbyist.” His firm’s website touts his “close relationships with key staffers on both sides of the aisle.” Smith has registered for three clients this year.

Smith said he did not report his work in 2012 under the LDA because most of it was focused on state lobbying. “When you’re not doing any federal lobbying, why keep registering for no good reason?” he asked.

Monte Ward, president of the American League of Lobbyists, said he sees multiple factors at play in the downturn in LDA revenue, including a tough economy. But during a Web chat discussing the study Wednesday, he noted that registered lobbyists such as himself are “very concerned with those lobbyists that are flying under the radar and not registering.” (This reporter participated in the Web chat.)

The ALL and groups such as the American Bar Association have proposed tightening what they view as loopholes, such as the 20 percent threshold, in the lobby disclosure law.

Timothy LaPira, a political science professor at James Madison University, said he believes the declining number of registered lobbyists stems from a 2007 expansion of the lobbying disclosure law that toughened penalties, increased reporting requirements and charged the Government Accountability Office with conducting annual audits of lobby reports. That, combined with President Barack Obama’s ban on hiring most lobbyists for jobs in his administration, may have led to people de-registering.

LaPira noted during the online chat that the GAO is only required to follow up on lobbying reports that are filed.

“Congress did not require them to investigate those who do not register,” he wrote. “The consequence — intended or not — is that we now have less transparency about what most people would think of as lobbying influence, not more.”