Virgin Media has slammed online broadband speed tests, claiming they are inaccurate.

The tests, which usually involve timing how long it takes to download a file to a PC, help consumers discover if the speed they're getting matches those promised by their ISP. However, according to the BBC, Virgin Media claims the files sent are often too small to provide an accurate result.

The comments come as Virgin Media prepares to launch its 50Mbps service, and the ISP fears that the error margin on current tests will be increased at faster speeds, resulting in even more inaccurate results.

The ISP has also voiced its concern over the bottlenecks and delays caused when a number of people use a particular broadband speed test at the same time, and said that tests using hardware directly attached to a modem, like those from SamKnows, gave more accurate results.