UK 3G operator 3 has announced a new pricing plan for mobile data - a flat £5 a month for what is being billed as unlimited data.

3 has become the first mobile operator to offer unlimited mobile internet access to all its contract customers.

This new package comes on the back of the success of 3's X-Series, launched with the Nokia N73 last December. The £5 flat rate, unlimited mobile internet service will be open to contract users with any recently launched 3 handset.

I'll do some investigating, as offers of "unlimited" data have a history of not actually meaning "unlimited", but rather "limited to an amount we won't tell you about except in the small print".

Via SMS Text News and the evening newspapers.

Update: A quick trawl through the terms and conditions shows that "unlimited" is actually "1Gb a month" under 3's fair use policy.

Unlimited Data

Fair Use Limit: 1 GB each month

X-Series - 1 GB should be more than enough to allow you to surf websites, use ISP email and download podcasts

X-Series Silver & Gold - 1 GB should be more than enough to allow you to surf websites, use Mobile Mail and download podcasts

We will let you know by text message once you have reached the fair use limit and ask you to cease using the included data services for the remainder of the month. If you continue to use the services we may suspend your data usage until the next month. This will not impact your access to other X-Series services.

Fair Use limits also apply to other data-based services advertised as unlimited, such as MSN Messenger, limited to 10,000 messages a month, and Skype, limited to 5,000 minutes a month.