"The Vice President has retained Richard Cullen of McGuire Woods to assist him in responding to inquiries by the special counsel", Pence communications director Jared Agen said in a statement yesterday.
Pence's move follows a decision by President Donald Trump to hire outside counsel Marc Kasowitz and could signal the investigation is entering a new phase.
"The FBI leak of information regarding the president is outrageous, inexcusable and illegal", Kasowitz's spokesman Mark Corallo said to the Post. Cullen referred questions to the vice president's office.
Cullen, a former Virginia attorney general, served as the US attorney for the Eastern District of Virginia under President George H.W. Bush and worked on President George W. Bush's legal team during the Florida recount in the 2000 presidential election. They declined to say what had sparked Pence's decision to hire an outside lawyer and referred all questions concerning the Russian Federation investigation to Cullen's office.
An aide tells NPR the decision to hire an outside lawyer has been under consideration for weeks, and Pence chose to go forward with it earlier this week.
On Wednesday, the Washington Post reported that Mueller is investigating Trump for possible obstruction of justice in the Russian Federation investigation. Flynn was forced to resign after misleading Pence about his contacts and conversations Sergey Kislyak, Russia's ambassador to the USA, during the transition.
Mueller and congressional committees are investigating Russian meddling in the 2016 election and possible connections with Trump's campaign.
Trump ultimately fired Flynn for misleading the vice president.
Scrutiny of the president's actions has intensified since he fired Federal Bureau of Investigation director James Comey last month.
Pence's choice for outside counsel contrasts with the president's. But he never hired a counsel during the investigation and subsequent impeachment of President Bill Clinton.