The cuts, which will be spread across the country, represent 7.5% of the company's 16,000-strong workforce.
The move follows the merger earlier this year of the two networks which together have 30 million customers.
At the time analysts warned the move would mean some staff overlap and would therefore mean a reduction in staff numbers.
The jobs will go from back office, headquarters and management.
The group said no cuts would be made among customer service or store staff.
Its main offices are in London, Bristol and Hatfield, Hertfordshire.
Everything Everywhere, the company that runs Orange and T-Mobile in the UK has said that it will cut 1,200 jobs.