BT says it expects to have cut 10,000 jobs by the end of the financial year.
The cuts will mainly affect agency and contract staff and offshore workers, the company said.
The company said it had already cut 4,000 jobs, leaving a further 6,000 to go by the end of March. BT has a global workforce of 160,000.
The cuts were not a "direct result" of the economic downturn, said Ian Livingston, BT's chief executive.
"This is a reflection of the fact we have to become leaner," he told BBC News.
"We need to do it in good times and bad."
The UK's unemployment rate jumped to its highest in five years in October as more firms cut jobs to cope with the economic slowdown.
However, the job losses, which will lead to lower costs, cheered investors.
BT shares were up 12%, or 13.5 pence, at 126p.
'Decisive action'
BT said that three of its four main business units were performing well, but said profits at its global services division "were simply not good enough".
"We are taking decisive action to put matters right," Mr. Livingston said.
The firm said it had already replaced the head of the division.
The job losses come as the firm announced a 11% fall in pre-tax profit for the July to September quarter.
Pre-tax profits totalled £590m and the firm said revenue rose 4% to £5.3bn.
Last month, BT had warned that its global services division, which provides IT networks to multinational businesses, would report lower profits. Its shares fell nearly 20% on the news.
The company announced radical changes to its pension scheme this week, including an increase in the retirement age from 60 to 65 and breaking the link between final salaries and pension payments.
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