The US firm has begun viewing alternatives to its existing offices in Tower 42 with a view to using a break clause in its lease next year, otherwise the lease would expire in 2009.
Orrick real estate partner Anne O'Neill, who is overseeing the review, said the firm requires further space in order to facilitate its ongoing expansion campaign. The London office more than doubled in size to 50 lawyers last year.
O'Neill said the firm is now working to a five-year plan, confirming comments made by London head Martin Bartlam earlier this year that Orrick was now looking to bed down its recent growth.
O'Neill said that the firm had not yet finalised exactly how much extra space it required, although it is likely to total around 45,000sq ft. This is almost double the size of its current premises.
One property surveyor said the current top-of-market rate within the City is £55 per sq ft, although Orrick was likely to secure a discount or rent-free period. At this rate, without a discount, the space required would cost £2.47m a year.
O'Neill said she hoped to complete the review within the next three to six months. She would not confirm whether the firm would definitely move, but did admit she was in negotiations on other premises.