Energis is axeing up to 350 jobs to cut around £20 million a year in overheads.
More than 250 of the jobs will be lost in the UK with the rest coming from at the business telco's European operations.
At the moment it's not known where the axe will fall and indications of the cuts won't be known until the company begins its consultation period with employees.
Staff were told of the cuts - which come on top of 100 redundancies announced earlier this year as part of Energis' European integration programme - on the day the company announced its interim results for the six months to September 30.
Turnover for the six months ended September 30 was up from £368 million in 2000 to £487.9 million this year.
Pre-tax losses over the same period more than doubled from £45.3 million to £96.7 million.
David Wickham, chief exec of Energis, said: "The market for business telecoms has changed fundamentally compared with last year.
"We have also witnessed a slow-down in the growth of usage of telecoms by some customers and, in a few cases, a reduction, reflecting these customers' current levels of trading activity," he said.
However, the company is confident that a change of strategy which sees it provide telecoms services and products that help other companies cut costs will lead to increased sales.
By early afternoon Energis shares were up 3.5p (4.27 per cent) to 85.5p. ®