Three has announced plans to offer a £3 supplement to all its pay monthly smartphone customers giving them unlimited data to chomp through.

The new add-on comes as Three's research tells it that smartphone users' average data use is on the up and up.

Three's iPhone 4 customers were using an average of 488Mbps of data per month in February 2011; by August they were using nearly 1.2GB a month, which is well over what most networks class as 'unlimited data'.

Of course, it's worth noting that these results could be skewed by iPhone 4 users already on Three's all-you-can-eat data plans who are munching through data with gay abandon.

The whole internet for £3

But with data-hungry apps, streaming and downloads proving ever more popular, we wouldn't be surprised to see smartphone users getting through more and more data all the time.

"The One Plan quickly became our number on contract tariff and our all-you-can-eat PAYG offer is our most popular bundle," said Thomas Malleschitz, marketing director at Three UK.

"Our customers tell us that their use of data goes up significantly over the lifetime of their contracts, as they do more and more with their handset. All-you-can-eat data means that they don't have to worry, they can have that peace of mind for the long term on a contract of their choice."