A recent survey by Wired magazine has pointed to mobile carriers as the reason for the iPhone 3G slowdown.

The magazine asked some 2,600 iPhone 3G users around the world to contribute 3G performance numbers from their localities.

The results, claims Wired, suggest that the sluggish 3G speeds have more to do with the local 3G networks than any shortcomings in the hardware.

3G performance has by far been the biggest complaint from users ever since the iPhone 3G was launched in early July. The model was the first to run with a 3G connection, eschewing the EDGE network hardware employed by the previous model.

So far, nobody has been able to pinpoint the exact reason for the slowdown. One analyst firm has suggested that the problems were due to bad hardware from Infineon. Other pundits suggested a firmware issue which they say Apple attempted to fix with the last update.

However, according to Wired the carriers are the ones to blame, not Apple.

"In our view, this data is a strong indicator that performance of the mobile carrier's network is affecting the iPhone 3G more than the handset itself," read the report.

"Altogether, this furthers our thesis that it's highly unlikely that Apple is going to wave a magic wand and say, '3G problems, be gone,' with a software update."

The survey also found that the fastest 3G speeds were being reported on T-Mobile's networks in Europe, while Australian carriers Optus and Virgin reported the slowest 3G speeds.

The United States reported the most instances of no 3G connection available, not surprising given that 3G networks are relatively new in the US and unavailable in many of the more remote parts of the country.