Shearson Lehman International said it was firing 150 employees in London in a move linked to the "Big Bang" deregulation that revolutionized the London's stock exchange last year. A spokesman said the cuts stemmed from the consolidation of the group's business in Britain into one office from five and changing conditions in London security markets following deregulation. The unit is part of the Shearson Lehman Bros. investment house, which is owned by American Express Co. The spokesman said Shearson was not closing any operational sectors, but said there would be layoffs in a number of areas, including in government bond and equity sales. No corporate finance staff members are being fired.