BT has announced plans to cut 13,000 jobs during the next three years as part of its restructuring plan to invest in the next generation of mobile networks and ultrafast broadband.

Britain’s largest telecoms operator said that the greatest impact of the cuts will fall on back-office and middle management roles. The company added that about a third of the eliminated positions will come from its Global Services division based outside of the UK.

BT also said that it plans to vacate its existing headquarters in central London and move to smaller premises.

On a positive note, the company added that it will hire about 6,000 people in customer service, front-line engineering and cybersecurity roles.

The estimated total cost of the restructuring is £800m, but operating costs should decrease by £1.5bn when it is complete.

BT will increase its annual investment to around £3.7bn, with a focus on “ultrafast broadband and taking a lead in 5G.”

In a statement, the company said: “This plan will help BT become a leader in converged communications, continue to power the UK’s digital economy, and drive greater value for shareholders.”

Philippa Childs, General Secretary of the Prospect Union, said that the proposed job cuts are “a devastating blow to managers and professionals represented by Prospect.” She added that the scale of the proposed cuts is higher than expected and that the loss of highly skilled employees will hurt BT’s capabilities in innovation and research.

BT promised to decrease a £11.3bn deficit in its pension fund by making a payment of £2.1bn by 2020 and issuing a £2bn bond to cover an additional part of the deficit.