While the credit crisis has produced a steady stream of layoffs as write-offs force Wall Street to prune headcount, a London-based bank is adding U.S.-based security analysts and bankers.

Collins Stewart is using the weak dollar and cutbacks at rival firms to beef up its New York team, reports Crain's New York Business. Over the last 12 months it's made as many as 60 hires in New York – but "total headcount has only risen by about a dozen as it weeds out low producers," the story notes.

Shawn McLoughlin, Collins Stewart's chief executive of the Americas, told Crain's the firm is "in a building mode." During the past month the bank has added energy and biotech research analysts, and plans to move into derivatives and merger advisory services.

The moves highlight the firm's rapid expansion in the U.S. In June, it hired a team of oil analysts from the boutique Ferris Baker Watts, and a group of biotech analysts from Jefferies & Co. Earlier, it tapped a team of New York-based bankers to uncover business opportunities in China.

Collins Stewart substantially expanded its presence in the U.S. in July 2007 when it acquired investment bank C.E. Unterberg Towbin for $32 million. Today, the firm has 175 U.S. employees, based primarily in New York. The firm was founded in 1991 and operates globally in 12 offices. Its core products include capital markets, securities, advisory services and wealth management. In addition to oil and biotech, the firm's research team covers technology, healthcare, defense, Internet and media.