The company said the job losses would mainly affect back office and middle management roles, with two thirds of the cuts set fall on UK staff.
Remaining staff cuts are expected to impact upon BT’s operations abroad.
The business also plans to quit its central London headquarters.
The move comes as BT looks to cut costs by around £1.5 billion by the final year of its three-year plan.
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The telecoms firm added that it would be hiring around 6,000 new employees “to support network deployment and customer service”.
BT has around 106,400 employees globally, with 82,800 in the UK.
The FTSE 100 firm saw its shares tank on the news, falling as much as 8.8% at the start of trading.
The announcement comes nearly a year after the company said it was to axe 4,000 jobs as part of a restructuring of its Global Services unit.
BT chief executive Gavin Patterson said: “Decisions like this are not easy.”
“We recognise that it is going to affect a lot of people, but ultimately we need to do these things to ensure that we remain a competitive business going forward and that we can benchmark our performance against peer companies,” he told reporters.
He added that it was the “right thing for the business” and helps take BT “into its next chapter”.
BT explained on Thursday that it was making moves to simplify its operating model by “de-layering” its management structure and ensuring there are “fewer, bigger, more accountable leadership roles”.
It was also trying to improve productivity across its core UK operations, including “process simplification and automation to reduce costs”.