BT has been named the ISP with the worst call centre that keeps customers waiting longest.

Consumer organisation Which? surveyed some the biggest broadband suppliers, banks and energy companies, by making some 500 calls to their customer service centres. BT's broadband call centre came out as the worst with the longest waiting a whopping 13 minutes and 49 seconds. Which? also said that while the call was free for those calling from landlines, it would have cost £2.08 for those on a typical mobile phone tariff.

Sky came second, with a nine minute and nine second wait, and a call cost of 61p from landlines, or £2.29 from a mobile. Virgin Media followed closely behind, as it took eight minutes and 49 second to talk to a customer service representive at a cost of 47p from landlines or £2.21 from mobiles.

"If you're not happy with the way your call has been handled, keep a note of the people you've spoken to and the time and date of your call. If you want to escalate things, speak to a supervisor," Which? said.

"Knowing how much you will be charged for making one of these calls is not simple. Where possible, providers should use low-cost phone numbers for their help lines"

Helen Rutherford, director at IT services company 2e2 said it was clear many businesses must still improve their call centre operations, as waiting for almost a quarter of an hour in this day and age is unacceptable.

"Businesses need to improve their overall customer experience; otherwise they will find that customers will vote with their feet and move to a competitor. Today's businesses need to be contactable 24/7 so they need to have a joined up customer service operation, which gives customers the opportunity to contact them either on the phone or, increasingly, over the web," she said.

"It also means ensuring call centre agents have access to the right information when customers call, as there is nothing more frustrating than being passed on from pillar to post when trying to get a customer service issue resolved. "

Rutherford said businesses should be embracing the latest call centre, CRM, instant messaging (presence) and self-service technologies.

"When business adopt this multi channel approach, call waiting times will in time resolve themselves as customers who really need to speak to someone will be the only ones calling through. Those businesses that this take approach will increasingly be the winners, in an increasingly competitive battle for customers."