A Northern Virginia Democrat and candidate for attorney general wants a federal probe into a Virginia-based supplement maker whose close ties to Attorney General Ken Cuccinelli and Governor Bob McDonnell have come under close election-year scrutiny.

Sen. Mark Herring, D-Leesburg, wrote to the Justice Department's Public Integrity Section Thursday asking for an investigation of Star Scientific and its CEO, Jonnie Williams Sr. The company's "cozy relationship" with Cuccinelli and McDonnell raises ethical concerns that warrant outside, independent review, Herring said.

Star Scientific is currently in a legal battle with the state over $700,000 in back taxes, though the case has been dormant for several years. Cuccinelli owns more than $10,000 in Star Science stock, some purchased after the company sued the state, and has accepted $13,000 in gifts from Williams. McDonnell considers Williams a close friend and has personally helped market Star Scientific's tobacco-based anti-inflammatory supplement.

Williams paid the $15,000 catering bill for the wedding of McDonnell's daughter in 2011. McDonnell did not report the gift on his financial disclosure forms that year, noting Virginia law exempts gifts to family members from disclosure.

"Accepting gifts from a company that has business before the state raises serious ethical questions and concerns, and the people of Virginia deserve a fair and independent investigation to determine the facts," Herring said.

Herring is running for state attorney general this year, competing for the Democratic nomination against former federal prosecutor Justin Fairfax. The Loudoun County lawmaker has frequently ripped into Cuccinelli to score points in the race and has often criticized the two Republicans in the race, Del. Rob Bell and Sen. Mark Obenshain, as Cuccinelli clones.

Cuccinelli, a Republican candidate for governor, shrugged off Herring's calls for an investigation as a "distraction" by the attorney general's Democratic opponent Terry McAuliffe.

"No matter how hard the McAuliffe campaign might try, there is no conflict of interest involving the attorney general, period," Cuccinelli spokeswoman Anna Nix said. "Virginians are not buying this shameful ploy."