The new ad is coming to billboards

The group, whose hold over directory enquiries was ended in August when regulator Oftel opened up the market to 15 new entrants, is to push a new advertising campaign for its 118 500 service.

As part of the �3m push, advertisements will appear on 5,200 poster sites nationwide from Monday.

BT said last month that the number of callers ringing directory enquiry telephone services had halved since the introduction of the new 118 numbers.

Daylight robbery

BT argues that deregulation of the old 192 service, which was intended to benefit consumers, has instead seen the sector contract while callers get an inferior service from new operators.

In the run-up to switching off 192, David Edmonds, the Director General of industry regulator Oftel, pledged that deregulation would offer consumers "real choice" for the first time when calling directory enquiries.

Concerns have also emerged about the quality of some of the new services and confusion caused by the plethora of new numbers.

Consumer watchdogs have branded prices charged by some operators as "daylight robbery".

"Call costs rise"

One survey claimed that the cost of calling directory enquiries has risen by up to 50% since the 118 services came in and an average of only two out of three enquiries had resulted in the caller being given the correct number.

However, BT claimed it was quicker and more accurate than its two main rivals, The Number's 118 118 and Dublin-based Conduit's 118 888.

It said an ICM survey had shown that BT scored a 98% success rate for finding residential numbers compared with The Number with 89%, Dublin-based Conduit with 80% and Yellow Pages at 91%.