O2 is the first UK network to unveil pricing for its iPhone 4 tariffs.

Apple's latest smartphone will be available on either 18 or 24 month contracts, with prices starting from £25 for 100 minutes of calls and unlimited text messaging.

However, the network has also chosen to cap its once 'unlimited' data offering. Users paying between £25 and £35 per month on a 24 month contract or between £30 and £40 per month on an 18 month contract have a data allowance of 500MB per month.

O2 reveals iPhone 4 UK tariffs

Those whose tariffs offer 900 or 1200 minutes per month will find their data is capped at 750MB, while those on the 'unlimited' monthly contract have a 1GB data allowance.

Alternative, O2 customers can purchase the handset themselves and then purchase one of O2's Simplicity tariffs. These start from £15 per month and users can choose between being tied in for 30 days or a year. The unlimited WiFi use remains.

O2 has also revealed details of its 'Early Upgrade Offer' that will allow its customers whose existing mobile contract has not yet expired to get their hands on an iPhone 4.

O2 said that instead of paying off the remaining contract in full, it will let its customers that want to take out a new iPhone 4 contract pay a one-off charge based upon a £20 per month fee for each full month left to run on the contract.

O2 customers interested in upgrading can visit the network's dedicated upgrade web page and enter their upgrade date to get an estimate as to how much the one-off charge will be.

O2 has not revealed how much the handset will cost to purchase outright, or the contribution mobile phone users on monthly contracts will have to make towards the phone.

From October, the network will allow users to purchase a bolt-on that offers an extra 500MB of data per month for £5, or an extra 1GB for £10 per month.

Apple's latest smartphone was unveiled by Steve Jobs this week at the company's Worldwide Developers Conference (WWDC).

The new handset, which features an all-new design, has "well over 100 new features" including an HD screen, video calling, a gyroscope, a new iMovie app and countless other upgrades.

However, the network did say the scheme could not be used in conjunction with an early upgrade eligibility that might already exist.

The iPhone 4 will be available from O2 stores, its website and branches of the Carphone Warehouse and Phones4U from June 24.

Check out the latest up-to-date information on iPhone 4 pricing and networks.