Carphone said it would not be shutting any stores
Mobile phone retailer Carphone Warehouse says 450 jobs are "at risk" following a review of the business.
Carphone - which also owns the TalkTalk broadband business - said it had begun talks with staff at its head office in North Action in west London.
It is also consulting with workers at call centres in Preston, Warrington and Wednesbury in the West Midlands.
The company said that its store workers would not be affected, and none of its High Street outlets would be closed.
It added that its planned opening of new stores in partnership with US retailer Best Buy would not be affected. It intends to open 100 Best Buy stores in Europe by 2013.
Carphone sold a half share in its retailing business to Best Buy for £1.1bn in May last year.