Lehman Brothers has doubled the time bankers must serve in order to claim their full entitlement of stock options on retirement.
Banking sources said bankers must serve a minimum of 10 years, with their age and length of service equalling 55, to claim full retirement benefits. The changes follow Lehman's recruitment drive in Europe, where it has hired some of the industry's brightest stars and paid them guaranteed retention bonuses.
Lehman staff own a large portion of the bank's equity, which has grown faster than its rivals in the last decade. One rival said: "This stops the new hires leaving once their two-year guarantees have run out."
One senior banking source said: "Bankers will be entitled to full benefits. It just defines more closely what the minimum length of service is. Before, length of service and age simply had to add up to 55."
Lehman would not comment.