A surge of lobbyists has left K Street this year to fill jobs as high-ranking staffers on Capitol Hill, focusing new attention on the dearth of rules governing what paid advocates can do after moving into the legislative world.

Ethics rules sharply limit the activities of former lobbyists who join the executive branch and former lawmakers who move to lobbying firms. But experts say there are no limits on lawmakers hiring K street employees and letting them write legislation in sync with the policies they advocated for hire.

New tallies indicate that nearly half of the roughly 150 former lobbyists working in top policy jobs for members of Congress or House committees have been hired in the past few months. And many are working on legislative issues of interest to their former employers.

The House Energy and Commerce Committee, for example, which led other House panels by hiring six lobbyists this year, is drafting legislation sought by oil and energy firms. At least four staffers on the committee payroll worked for those industries last year.

Washington has long had a revolving door between advocacy and government work, with a steady stream of lawyers, lobbyists and corporate officials moving between the public and private sectors. But the trend picked up on Capitol Hill this year, when an influx of more than 100 new lawmakers provoked a round of hiring by newly named Republican committee chairmen in the House.

House Speaker John A. Boehner (R-Ohio) employs four ex-lobbyists, who advise him on issues including telecommunications to energy. His chief policy adviser, Brett Loper, was lobbying last year against the president’s health-care legislation on behalf of the medical-device industry. This year, he is helping to organize legislative efforts to undo the new law.

Loper, who declined to comment for this article, filed a voluntary disclosure letter with House ethics officials pledging to recuse himself from “issues specific to his former employer,” said Boehner spokesman Michael Steel.

Steel said Loper will continue to work on a health-care repeal and related issues that don’t directly affect his former employer.

GOP legislative aides say lobbyists are often desirable hires because they have deep experience in the policy details surrounding major issues. “We try to hire the smartest, most talented people we can for every staff position,” Steel said.

But critics say the practice can create conflicts of interest, especially if staffers plan to return to lobbying jobs.

“The bottom line is that many of the most powerful congressional staffers, who are now responsible for working on behalf of the public’s interest, used to make a living convincing the government to benefit a client’s special interest,” said Sheila Krumholz, executive director of the Center for Responsive Politics, which this month released a list of former lobbyists who are working on lawmakers’ personal staffs.

More than four-fifths of the lobbyists hired this year for top jobs on personal staffs went to Republican offices, partly because of openings created when the GOP won control of the House in the midterm elections. Some aides said Republicans are more likely than Democrats to turn to those who lobbied on behalf of trade groups and corporations because of the party’s close connections to business groups.

But Democrats also have hired former lobbyists.

Richard J. Meltzer, the policy director for House Minority Leader Nancy Pelosi (D-Calif.), was a lobbyist until 2009 for oil and gas companies, hospitals, insurers, investment banks and nearly a dozen other large industries.

Drew Hammill, a spokesman for Pelosi, said policy aides are required to disclose any potential conflicts involving former employers, but the need for Meltzer to recuse himself “has not arisen.”

Of the 128 former lobbyists employed as chiefs of staff or legislative directors, 50 were hired this year, according to the CRP data. An additional 20 or so have recently joined committee staffs, a Washington Post survey shows.

Many who left lobbying jobs to work in Congress took substantial pay cuts.

Howard Cohen, for example, the chief health policy director for the Energy and Commerce Committee, headed a lobbying firm that was paid more than $1 million by hospitals, drugmakers and health-care groups for his advocacy work last year.

The maximum salary for House staff members in a personal office is $168,411; the figure for committees and leadership offices is $172,500.

Other former lobbyists working for the committee include its staff director, Gary Andres, who last year lobbied for health, railroad and credit card firms, Federal Express, General Motors and Google; and committee general counsel James D. Barnette, who lobbied last year for insurance, oil and gas, convenience store, liquor and timber companies.

Rules cover only departing — not arriving — senior congressional staffers, prohibiting them from lobbying a lawmaker’s office during a one-year “cooling-off period.” Retired House members also face a year-long ban, while former senators are required to refrain from lobbying for two years.

These and other restrictions were strengthened under a 2007 ethics measure co-sponsored by then-Sen. Barack Obama (D-Ill.). As president, Obama has barred registered lobbyists from being hired by agencies they lobbied without a special waiver. He also set a two-year ban for those who leave the administration on lobbying the agency that employed them.

Congressional staff members and lawmakers are barred from taking actions that benefit their personal financial interests. But “it’s a world of difference in approach” between the strict rules that govern work by ex-lobbyists in the executive branch and those in Congress, noted Kenneth Gross, an ethics lawyer who formerly headed the Federal Election Commission’s enforcement office. “The legislative branch should have rules that are much tighter.”

David B. Krone, the chief of staff to Senate Majority Leader Harry Reid (D-Nev.) since 2010, was a telecommunications lobbyist until 2006 and then a Comcast executive. In Reid’s office, he has worked on telecommunications issues such as net neutrality and a new cybersecurity bill.

He declined to comment, but Reid spokesman Jon Summers said Krone “has worked closely with Reid on every issue.”

When Rep. Michael C. Burgess, a Republican doctor from Texas, sponsored a bill last month that would make dental schools eligible for emergency preparedness funding, his chief staff adviser on health issues was James Paluskiewicz, a lobbyist until 2008 for the American Dental Association. The association had endorsed the bill, which the House passed on March 8.

Paluskiewicz declined a request to comment. But Whitney Thompson, Burgess’s spokeswoman, said: “There is no conflict. . . . Burgess supports [the bill] because it expands federal resources and is intended to strengthen medical responses during disasters.”

In February, when Rep. Jo Ann Emerson (R-Mo.) sponsored a spending bill provision to stop enforcement of a key component of the new health-care law, her principal health policy adviser was Christina Lucas. Until August, Lucas was a lobbyist for an Indiana hospital chain that opposed the Obama health-care legislation.

Lucas declined a request to comment. But Jeffrey Connor, Emerson’s chief of staff, said that Lucas had not lobbied the congresswoman previously and that Emerson had not changed her position. “If you look at the congresswoman’s record on the health-care bill, she is extremely consistent in her opposition to it,” he said.

Michael Bloomquist, deputy general counsel for the Energy and Commerce Committee, lobbied last year on four bills that were before the panel, according to lobbying disclosures. Committee Chairman Fred Upton (R-Mich.) recently introduced a new version of one of those bills, which would delay new regulation of greenhouse gases by the Environmental Protection Agency. An energy subcommittee approved the measure last week.

Maryam Brown, the committee’s chief energy counsel and one of those who helped draft the legislation, was paid more than $270,000 as a ConocoPhillips lawyer in 2009 and 2010, according to House records. The company’s chief executive argued before the committee in 2010 against EPA regulation of greenhouse gases, saying it was the “wrong way” to deal with climate change.

Environmental advocates and others opposed to the legislation have pointed to some of Upton’s new committee staffers as a problem.

“Quite literally, the people from ConocoPhillips and all these other energy companies are now sitting at his desk and helping to write legislation that will have a direct impact on the bottom line of energy companies,” said Melinda Pierce, deputy director of national campaigns at the Sierra Club.

Bloomquist and Brown declined to comment, but committee spokeswoman Alexa Marrero said the panel “has a large, talented staff from a wide range of backgrounds, including individuals who have expertise on U.S. energy policy.” She said that Upton requires staff members to recuse themselves from issues that specifically affect a former employer but that Brown was not recused because “ConocoPhillips would not be affected differently than any other organization.”

Bloomquist, she said, has a “largely parliamentary role,” rather than a policymaking role.

Research editor Alice Crites contributed to this report.