The company, which has over 5,000 staff, serving 13.6 million customers across London and the Thames Valley, said the majority of the posts would be in support functions.
"We have been planning a remodelling of the business, to be rolled out this year, which will allow us to meet future challenges,” said CEO David Owens. "A number of redundancies had always been planned as part of this restructuring process, however, the recession, which is reducing our revenue, and driving up borrowing costs, has meant that we have had to bring this redundancy programme forward."