The firm is consulting with employees on plans to move its global headquarters in Henrietta Place, just off Oxford Street, to its existing office in Park Royal, west London.
"We cannot comment on what the specific numbers of employees affected will be. Our plans involve a complex combination of factors to achieve the cost savings we have targeted, which will vary market by market," a spokeswoman said.
The major restructuring plan will begin on July 1, and is designed to save £100 million in the 2010 financial year.
"The savings will come from costs of goods sold and overheads - which include running costs, facilities and employees - and contributions to these savings will come from most parts of the business around the world.
" We will observe all our obligations in respect of consultation which may apply in a given jurisdiction."
The Henrietta Place offices will close by the end of 2009, she added.