Foster + Partners, the London-based practice founded by Pritzker Prize-winning architect Norman Foster, is laying off between 300 and 350 people due to the worldwide economic slowdown—a move that will reduce the company's workforce by nearly a quarter. The firm also is closing its Berlin and Istanbul offices, according to a spokesperson.

“A number of our international clients have fallen victim to the current economic climate, said the firm’s chief executive, Mouzhan Majidi, in a formal statement. “After the eventual necessity to make reductions the company will still be at a similar size to that of 18 months ago.”

The global credit crunch has impacted several of the firm’s projects, of which 80 percent are international. Financing difficulties led to the cancellation of its 118-story Rossiya tower in Moscow, which would have been Europe's tallest skyscraper, and left the $4 billion Crystal Island development, also in Moscow, in doubt. A 79-story high-rise at the World Trade Center in Lower Manhattan has been delayed, and the 49-story Harmon Hotel & Spa on the Las Vegas Strip has been scaled back due to rising construction costs and sluggish condominium sales.

Foster + Partners, unlike most architecture practices, has outside investors. London-based 3i Group PLC made a minority investment in the firm in 2007; its stake is rumored to be around 40 percent. Steve Nicholls, a 3i partner, sits on the board of Foster + Partners. The investment was meant to help underwrite 42-year-old firm’s growth into new markets. “Foster + Partners is still a key an investment,” says Rachel Richards, a 3i spokesperson. “That hasn't changed.”

The firm currently has 260 projects on the boards and 15 offices, including ones in New York City, Boston, and Houston.