Virgin Mobile has become the fourth telco to officially sell the iPhone 3G in Australia.

From today, consumers can purchase an iPhone 3G from Virgin. Running on the Optus network, Virgin Mobile is offering two plans, both on 24 month contracts and both with data plans much more competitive than Telstra, Vodafone and Optus — the three other telcos licensed to sell the iPhone in Australia.

The first plan costs $70 per month and includes $520 worth of calls and 1GB of data. The second costs $100 per month. It includes $520 worth of calls and a whopping 5GB of data.

The 8GB iPhone 3G is free on both plans, while the 16GB model is free on the $100 plan, but an extra $4 per month on the $70 plan. Both plans include free calls and messages to other Virgin Mobiles in Australia and free voicemail.

Stocks are limited — the 16GB model is currently only available in white, with Virgin claiming the black model is out of stock.

Following Virgin's announcement, 3 Mobile is the only telco in Australia that isn't currently selling the iPhone 3G. However, it is offering plans that target owners of iPhone 3Gs.