Royal Bank of Scotland Group Plc may have less capital than its largest peers and go back for more after raising $23.5 billion in Europe's biggest rights offering, according to Deutsche Bank AG.

Edinburgh-based RBS is the parent of Connecticut-based Citizens Bank, which has the second-largest bank-branch network in Philadelphia and its Pennsylvania suburbs, after Wachovia Corp.

RBS has lost 19 percent of its market value since it announced the rights offer April 22.