A John McCain adviser has been asked to leave the campaign following inquiries about the consultant's work with an independent "527" group that sharply criticized the Democratic presidential candidates, according to a report Thursday night by The Politico.

The adviser, Craig Shirley, was consulting McCain while his firm was also doing public relations work for the group Stop Her Now, according to the article.

The McCain campaign, in response, released a new policy stating that no one on the McCain campaign "may participate in a 527 or other independent entity that makes public communications that support or oppose any presidential candidate."

The campaign also has launched background checks of its entire staff, including a questionnaire inquiring about previous professional activities, in case any have connections to lobbyists, according to a blog report by Marc Ambinder at TheAtlantic.com.

The Stop Her Now group initially targeted Hillary Clinton -- in part through cartoons and animated features on its Web site -- but has changed its message to "Stop Him Now," going after Barack Obama as he's taken the lead in the Democratic contest. The top of the Web site now declares it is "saving America from the radical leftist agenda of Barack Obama."

Shirley was ousted after two other high-profile McCain aides resigned their positions following reports that they were working for a firm that did lobbying work with the Burmese military junta in 2002.

Newsweek initially ran a story questioning Doug Goodyear -- the man picked by McCain's campaign to run the 2008 Republican National Convention -- and his firm DCI Group's $348,000 contract with the junta. The article also drew attention to DCI's work with 527 groups.

Goodyear said he stepped down from his convention role "so as not to become a distraction in this campaign."

Click here to read the Politico report on McCain's adviser.