BT is to cut 13,000 jobs over the next three years, the telecoms giant has announced.

The company said most of the jobs lost would be back office and middle management roles, with a view to reducing costs by £1.5bn.

It also claimed it would be creating 6,000 new roles, “to support network deployment and customer service”. Previous reports had estimated the group was set to cut 6,000 roles.

Gavin Patterson, the company’s chief executive, said two-thirds of the job cuts will be made in the UK.

Philippa Childs, national secretary of Prospect, the union which represents a large number of BT workers, said the announcement would “come as a devastating blow to managers and professionals represented by Prospect”.

“It is particularly disappointing as Prospect has been working closely with BT to ensure that the impact of organisational changes including restructuring and re-organisation have been thoroughly examined, but this number sounds unrealistic,” she added.

“BT staff at all levels work tirelessly to provide an excellent service to customers. Many of the roles that BT is proposing to cut are highly skilled professionals and the loss of that expertise could impact BT’s research and innovation capability. We are also concerned that cutting such a large number of roles will inevitably impact those who remain in BT and could lead to work being pushed down to employees in lower grades.”

Ms Childs said Prospect would push BT to minimise job losses during the consultation period.

BT’s restructuring proposals come as the group continues to deal with the consequences of an accounting scandal at its Italian operation, which came to light last year. As well as drastic job cuts, there are also plans for BT to leave its headquarters in central London.

“Finding £1.5bn of cost cuts and moving out of its expensive London HQ to focus on 30 fit-for-purpose hubs is the kind of action BT shareholders have wanted to see for years,” said Lee Wild, head of equity strategy at interactive investor.

“Too long a bloated, lumbering beast, BT’s recognition that it must become a ‘lean and agile’ organisation is long overdue. It is both dramatic and far-reaching, yet both sensible and critical if the business is to compete with rivals who saw the future of a rapidly changing industry much quicker than BT.”

The company announced its plans as it revealed a 1 per cent drop in revenue for the year to 31 March, to £23.7bn, while pre-tax profit rose 11 per cent to £2.6bn.

Profit for the final quarter of the last financial year was up 98 per cent compared to the same period of the previous 12 months, at £872m.