Everything Everywhere, the new UK mobile JV, plans to axe 1,200 back office and middle management jobs by Christmas.
The reduction of the workforce by more than 7% is aimed at trimming £3.5 billion ($5.5b) in costs by 2014. It will bring total layoffs to 3,700 including former T-Mobile employees ditched after the merger with Orange UK was announced in September 2009.
Around 30 management positions have been cut since July when the merger was completed, the Telegraph reports.
News of the redundancies follows disappointing 2Q results - the first since the merger was completed, with revenue and ebitda both falling year-on-year.
Boss Tom Alexander said the redundancies were necessary to remove duplicate roles within the merged company and to improve efficiency, the Telegraph said.
While jobs are due to go across all departments, FT.com said the IT and legal departments would be hardest hit.
Although the carrier has entered a 90-day consultation period with its staff, the layoffs are likely to be completed by Christmas.