A warning we've heard before - ISPs are facing a sharp increase in bandwidth costs as internet TV services such as the BBC's iPlayer continue to grow in popularity.

Following the news from the BBC that during January, more than 2.2 million people watched a programme on the service, iPlayerInfo from ISP PlusNet shows that its streaming costs tripled during January, which was the first month that the iPlayer's streaming service operated.

The cost per user rose from 6.1p per month to 18.3p, which means that if PlusNet's figures are industry-wide, then the iPlayer added £1 million to ISPs' costs during January.

Ashley Highfield, the BBC's director of future media and technology, insists that iPlayer has had a "negligible impact on the UK internet infrastructure".