Faced with hiring a new administration, President-elect Barack Obama is learning how hard it is to keep his promise to avoid aides who have been entangled with the capital’s lobbying scene.

An Associated Press review of more than 400 members of Obama’s transition team identified at least 34 who have registered in recent years to lobby government officials on behalf of clients or employers — some as recently as this summer. The AP’s review represents the most comprehensive examination to date of people working on Obama’s incoming administration.

During the campaign, Obama promised to keep lobbyists at arm’s length, and he has taken steps aimed at keeping out the taint of the influence business. He imposed first-ever rules that prohibit anyone on his transition team from working in policy areas on which they had lobbied in the past year — an arbitrary time period — and a withdrawal system was set up for anyone who might run afoul of the rule.

Yet, as Obama is finding out, it is impractical to plan and fill up a new government without connections to lobbyists.

Among the AP’s findings:

• An Obama adviser on immigration issues, Maria Echaveste, lobbied for the United Farm Workers this year to protect immigrant agricultural workers as the Bush administration sought to ease hiring of seasonal farm labor and Congress debated an immigration overhaul. Echaveste, who worked in the White House and Labor Department under President Bill Clinton, assured Obama she will not weigh in on the farmworker visa issue that was her lobbying focus.

• The former Agriculture Department official leading Obama’s agricultural policy review, Bart Chilton, lobbied until last year as vice president of the National Farmers Union. It spends hundreds of thousands of dollars each year to press for farm subsidy programs, fighting the North American Free Trade Agreement and reducing taxes on farms and ranches.

• An Obama transition adviser for health and human services, Bill Corr, lobbied to prevent children from smoking as executive director of the Campaign for Tobacco-Free Kids. The group has spent $675,000 this year trying to influence policymakers. Corr has told Obama he will not offer advice on tobacco issues.

• A transition advisory board member, Mark Gitenstein, was registered until August to lobby on behalf of the U.S. Chamber of Commerce, AT&T Inc. and financial firms such as Ernst & Young LLP and Merrill Lynch & Co. Inc. Gitenstein is working on transition management issues, not specific policies, but has agreed not to deal with topics on which he lobbied.

Overall, the people Obama is relying on to build his administration have represented unions; energy, environmental groups, insurance, and drug companies; Wal-Mart; the National Association for the Advancement of Colored People; and the lobbying arm of the Washington-based Center for American Progress. The center is a think tank headed by John Podesta, former chief of staff to Bill Clinton and now co-chairman of Obama’s transition.

Also prominent on Obama’s new team are his big-money fundraisers. At least 18 of Obama’s major financial backers are helping him create his administration. They collected at least $50,000 each from friends and associates to help pay for the most expensive presidential campaign in history.

A few raised at least $500,000 each. They include two former officials from the Federal Communications Commission: Donald Gips, a one-time aide to Vice President Al Gore who is co-chairman of Obama’s teams reviewing government agencies; and Julius Genachowski, who was an executive at Barry Diller’s IAC/InterActiveCorp, when the Internet giant owned Ticketmaster and Home Shopping Network. Genachowski is working on technology and government reform policy for the new administration.

Despite Obama’s efforts to insulate his new administration from what might be tainted advice, lobbyists’ involvement in the new government warrants close scrutiny, said Sheila Krumholz, executive director of the Center for Responsive Politics, a nonpartisan institute that studies the influence business.

“They are taking a risk by taking these people on board,” Krumholz said. “If they’re viewed as being in the pocket of industry, that is not going to be beneficial to this administration that is trying so hard to claim a new mantle.”