The actress, who played the title character in Veronica Mars from 2004 to 2007, told Zap2it that she no longer has any desire to be "number one on the call sheet".
Bell said: "I'd been searching for the right TV project [and] I knew I didn't want anything built around me. [Being the lead is] a very different workload than number two."
She continued: "When you completely represent a show, there's so much more that's required of you. You're in every frame of the show, but there's also the publicity aspect that's a reality for us. There's just a lot more on your shoulders, a lot more pressure."
Bell added that she was eager to "have fun" on House of Lies, which stars Don Cheadle as a ruthless management consultant.
"I didn't want [the show] to be sold on me," she said. "I wanted to be part of a good project. And I trust Matthew Carnahan, our creator, implicitly. I think he's very funny, he's very dark [and] he's very provocative."
Dawn Olivieri, Ben Schwartz, Josh Lawson, Griffin Dunne, Nick Stahl and Michael Rady have also signed up to appear in House of Lies.
The show, which is based on Martin Kihn's book House of Lies: How Management Consultants Steal Your Watch and Then Tell You the Time, has been commissioned for 12 episodes by Showtime.
> Showtime picks up House Of Lies, Homeland
Watch a clip of Kristen Bell on Veronica Mars below: