WASHINGTON -- As Democratic presidential nominee Sen. Barack Obama targets his Republican rival Sen. John McCain for hiring former lobbyists to work on his campaign, a key member of Obama's campaign is paying a Washington lobbyist for legal advice: his running mate, Sen. Joe Biden.

Lobbyist William Oldaker continues to represent the Delaware Democrat in his simultaneous bid for Senate re-election, serving as legal counsel just as he has for Biden's campaigns for the past 25 years.

Oldaker is an election law attorney and partners with Biden's son Hunter at the Washington firm, Oldaker, Biden & Belair. He is also an appropriations lobbyist who represents lawyers, American Indians, and educational and health care institutions and who drew fire in 2005 for serving on numerous fundraising committees that donate to the lawmakers he lobbies.

Connections to lobbyists have been a hot-button campaign issue, with McCain and Obama both pledging to fight the influence of special interests in the White House.

Obama's campaign launched a multimedia assault on McCain last weekend, with two television advertisements, a new website, www.mclobbyist.com, and a Web video highlighting the seven former lobbyists who serve as McCain's top advisers.

"Who do you think will run his White House?" the voice in the ad asks.

Asked whether Oldaker's connection to Biden was appropriate given the ad campaign, a campaign spokesman emphasized Oldaker's credentials as an election law attorney in a statement.

"Bill Oldaker is the former general counsel to the Federal Election Commission, and his law practice for well over a quarter of a century has included prominent Democrats from a speaker of the House, to Senator Ted Kennedy, and General Wesley Clark," said Biden's spokesman David Wade. "Bill is as highly regarded a election law attorney as you'll ever find, and his firm continues to represent Joe Biden's Senate campaign."

However, Bill Allison of the Sunlight Foundation, a government watchdog group, said the same standard for a presidential campaign should apply to a Senate campaign.

"For someone who criticizes McCain for having former lobbyists who most likely will lobby again at some point at the top levels of his campaign, it seems completely inconsistent to have a running mate whose Senate campaign is being run by an active Washington lobbyist," he said.

Oldaker couldn't be reached for comment.

A 40-year Washington veteran, Oldaker is a founding partner of Oldaker, Biden & Belair and the co-located National Group lobbying firm, whose lobbyists represent the University of Delaware and submit requests for targeted spending items called "earmarks" to Biden's office.

Wade said Oldaker was present several years ago when Biden met with UD's president. Oldaker, however, does not lobby Biden or his staff, according to Wade.

Oldaker has served as a fundraiser for Biden and helped launch his political action committee, Unite Our States, which is no longer active.

He served as the PAC's assistant treasurer for a short time, but stepped down when government watchdogs assailed the practice of lobbyists signing off on political committees' contributions to other campaigns. A 2005 Center for Public Integrity study showed Oldaker was among the top lobbyists serving as treasurer on political committees since 1998.

"As the treasurer of 23 political committees, groups that raise funds to elect or defeat politicians, Oldaker has signed off on more than $2 million in donations since 1998 to the parties and candidates he is paid to influence," the group's report stated.

During his last presidential campaign, Biden paid Oldaker, Biden & Belair $133,377 for legal services, according to the FEC. His Senate campaign also paid the firm $9,104 for legal and accounting fees since late 2007. Earlier expenditures are not available electronically.

Delaware election law allows Biden to run for his seventh Senate term while running for vice president.

Hunter Biden has not received financial benefit from the firm's representation of his father, according to Wade. Hunter Biden had represented Oldaker, Biden & Belair and the lobbying firm on Capitol Hill, but severed ties with the National Group in 2006 before passage of a Senate ethics bill requiring senators to certify they or their family members would not benefit from directed spending items or tax benefits they are seeking, according to his father's Senate office.

Last month, Hunter wrote that he no longer expected to act as a federal lobbyist in a letter to the clerk of the House and Senate Office of Public Records that became public on Friday.