NTL has confirmed 6,000 jobs will be cut from its payroll of 17,000 as the cable company seeks to find £250m of savings before the end of 2007.
Some 1,535 employees will be taken on by IBM, which NTL already has an outsourcing deal with, while a "significant number" will go to other organisations that the company declined to name.
NTL said it expects natural attrition, voluntary redundancy and cutbacks in temporary staff will account for many more of the jobs it is sheddding.
While NTL didn't provide details, call centre workers are among those expected to be hardest hit. The decision to cut support staff may prove controversial in light of recent research into ISP customer satisfaction, which showed NTL had the lowest level of customer service and Telewest the highest.
NTL and Telewest merged last year, and this year announced the purchase of Virgin Mobile to add mobile services to their TV, phone and broadband offerings.
NTL chief executive Steve Burch said in a conference call that the integration with Virgin Mobile "effectively will be completed... by the end of 2007".
Neil Berkett, chief of operations at NTL, said in a statement: "Since we announced the merger with Telewest we have consistently said that headcount reductions are likely. We cannot avoid taking difficult decisions if it means a better experience for our customers in the long term. We recognise that today's announcement will mean uncertainty for some employees and the communities they live in."
This is the second round of large-scale layoffs for NTL, which cut its workforce from 21,000 to 13,000 in 2001 in an effort to tackle a £14bn debt.
There have been massive job losses across the telecoms sector. Orange announced 2,000 job cuts in the UK last week, while Cable & Wireless is shedding 3,000 positions.
NTL's redundancies came as the company revealed first quarter results for 2006. Revenue was £611m, up £127m on the previous quarter. NTL described the rise as "mainly due to the merger with Telewest".
The merger has also hit NTL's bottom line. The cable company reported £16.3m in merger and related fees, such as investment banking and insurance costs; £4.6m in costs from Telewest's long-term incentive plan; and £3.6m of consultancy fees for the merger integration.
Tony Hallett contributed to this report