Some of the biggest law firms are paying outsize salaries to star attorneys, in some cases 10 times what they give other partners, in a strategy that is stretching compensation gaps and testing morale at firms.

Washington litigator Jamie Wareham switched firms Monday, joining DLA Piper, where he will make about $5 million a year, a significant raise from his pay at Paul, Hastings, Janofsky & Walker LLP, where he was one of the highest-paid partners. Mr. Wareham, 50 years old, who has represented such clients as UBS and Chevron Corp., said he looks forward to helping “advance DLA's global platform.”

The pay package and others like it mark a departure for the $100 billion global corporate-law industry, which is still recovering from a prolonged downturn. While there has always been a pay gap at big firms, in the past partners with ownership stakes were paid relatively similar amounts to encourage a team approach and to ward off possible resentment.