More than 50 jobs will be cut when British Telecom closes its directory enquiries call centre in Cumbria.
The move will see 52 posts go at the offices in Barrow.
A spokesman for the company said the decision was regrettable, but necessary after a big reduction in call volumes as more customers used the internet.
The Communication Workers Union (CWU) described the move as a "knee-jerk" reaction that would be seen as a body blow to the community of Barrow.
In a statement, BT said: "BT is to close its directory enquiries centre in Barrow. 52 BT people are affected.
"We will be working to find new roles for all of the BT people wishing to remain with the company and, where appropriate, will provide re-skilling and re-training.
"The Barrow centre will close on 28 January, 2011.
"The whole directory enquiries industry, though still substantial and strong, is affected by a long-term trend of declining call volumes, stretching back well over 10 years, as it becomes easier for people to find numbers in other ways, such as the internet."
CWU deputy general secretary Andy Kerr said: "This is a knee-jerk reaction to a drop in one work stream.
"BT is a huge blue-chip company which could easily identify alternative work for the Barrow site so we believe the closure announcement is premature and a body blow to the local community."