In a statement, the group said it would kick off consultations with worker representatives at the end of January with a view of cutting “a maximum of 1,200” posts out of around 5,100 in Spain.
“In the current market context, demand for services is increasing exponentially but prices aren't: close to 50 percent of… memberships are associated with 'low and medium cost' offers,” the statement read.
It added that had caused a drop in revenues and profits “in the first six months of the current tax year.”
The group also said it needed to streamline the organisation.
The news comes after the British telecoms giant in November launched a new 1.2-billion-euro cost-cutting plan as it faced heavy losses.
Newly-installed chief executive Nick Read had said at the time that there were “challenging competitive conditions in Italy and Spain.”
Also on Thursday, Belgian telecoms operator Proximus announced it planned to cut 1,900 jobs over the next three years but pledged to recruit 1,250 other people over that period specialised in digital technology.
Proximus boss Dominique Leroy cited “aggressive market conditions… that leave us no choice.”