Its figures show that callers are more dissatisfied than ever with the cost and the poor level of service provided by the company, which last week announced annual profits of pounds 3.22bn - the equivalent of pounds 100 per second.
Consumer groups say the formal complaints, which have increased from an average of 12 per month to 38 in October alone, are just the "tip of the iceberg" and that BT will have to take drastic action if it is to compete with companies which Oftel is allowing to offer rival directory enquiries services from January next year.
The rise in complaints coincides with changes by BT to its directory enquiries facility, which came into effect at the start of October. These changes mean that operators will no longer provide customers with a residential phone number without being given a full address by the caller.
The operators also put customers through to a robotic voice to say there is no listing, and generally keep the length of the help time offered to a minimum of 25 seconds.
The company angered customers earlier this year when it decided to increase the cost of a 192 call by 40 per cent, from 25p to 35p. A call to international directory enquiries was increased from 20p to 80p.
"About five companies are waiting to compete with BT. We want to see a competitive market because one of the benefits to customers is that they will be able to pick the service they want," said an Oftel spokesman.
"BT are going to have to compete and provide a service that people will pay for. They will have to respond to the competition and improve their act and the service they offer."
The National Consumer Council agrees that BT is not giving customers value for money nor providing them with an adequate service.
"These figures are just the tip of the iceberg because there are many more people who are unhappy who do not make a formal complaint," added an NCC spokeswoman.
"Clearly this sudden surge in complaints indicates that there is something wrong and that BT has introduced changes which are not working.
"They say customers want a quicker service, but if someone is elderly or hard of hearing, then they will obviously need more time spent on dealing with their enquiry. We hope that BT will look into the complaints, especially given the fact that the service which was once free has risen in price."
A spokesman for BT admitted that there had been problems with its directory enquiries service, but said these had now been addressed. "The service has been revamped to help customers and not to hinder them," he said. "Our aim was to help customers by cutting down on the number of time-wasting searches and stop people being held in a queue. For example, if someone wants a number for a Mrs Jones who lives in Wales, then of course that is a futile search.
"We are always concerned if there are complaints, and in some circumstances our operators had not fully understood what they had to do. However, we handle millions of enquiries each year, and the amount of complaints is still very small."Reuse content