BRITISH Telecom has been named the worst offender in 25 years of investigations by consumer TV show Watchdog.

Customer complaints have led to the company being singled out 45 times in the show's history - almost twice as often as British Gas, which has featured the second most times.

It has made 27 appearances, closely followed by Tesco with 26.

In 1996 Watchdog investigated after a string of phone users, including comedian Barry Cryer, claimed BT was charging them hundreds of pounds for premium-rate sex-line calls they had never made.

The show claimed a telecoms expert it called in found that a new computer system had allowed hackers to tap into the software, make the calls and charge them to legitimate customers.

Confronted by Watchdog, BT said people were sometimes too embarrassed to admit they had made the calls, but agreed to remove the charges as a "goodwill gesture".

A BT spokesman said of the survey: "When you have 19 million customers mistakes will be made - all you can do is learn from them."

He added that the firm had recently been rated second for customer service in a survey of 25 telecoms companies by independent comparison website uSwitch.

The 10 companies featured most on Watchdog are:

1. BT (45 times)

2. British Gas (27 times)

3. Tesco (26 times)

4. Ford (24 times)

5. British Airways (20 times)

6. Thomson (18 times)

7. Airtours (12 times)

8. Barclays (11 times)

9. Boots (11 times)

10. Sainsbury's (11 times)