Bannon's hiring of Burck was first reported by the Daily Beast.
Burck, co-managing partner at the firm Quinn Emanuel, is also representing other key members of Trump's campaign and White House staff, including former chief of staff Reince Priebus and White House Counsel Donald McGahn.
The person familiar with the arrangement said Burck's representation is limited to congressional testimony and does not include preparing Bannon to speak to special counsel Robert S. Mueller III. It also covers only Bannon's role on Trump's campaign, as opposed to events that occurred during the presidential transition or while Bannon served as a top aide to Trump in the White House.
Earlier this week, Bannon was forced to leave his role as executive chairman of Breitbart News, the conservative outlet whose platform propelled him to national prominence, in the wake of anger from the White House about comments he made in a new book by journalist Michael Wolff, "Fire and Fury."
In the book, Bannon said it was "treasonous" of Trump's son Donald Trump Jr. to accept a meeting with a Russian lawyer in June 2016 who he thought would provide damaging information about Democratic candidate Hillary Clinton as part of a Russian government effort to help his father's campaign.
After the book's publication, Bannon expressed regret about his statements, saying his criticism was aimed at Paul Manafort, Trump's former campaign chairman, who also attended the meeting. He called Trump Jr. a "patriot."