The next-generation iPhone will launch on 21 November, it has been claimed.

According to technology magazine and website T3 a member of staff at mobile phone retailer Phones4U gave away the launch date as Monday 21 November.

The report intimates that the information was picked up at Phones4U's St Albans store, where it was also suggested that the next-generation iPhone - whether it will be called the iPhone 5 or iPhone 4S - would be available on tariffs similar to those offered at the launch of the iPhone 4.

However, there is a lot about this story that doesn't add up. It seems wholly unlikely that all but the most senior of staff at Phones4U would know the launch date of the next-generation iPhone - that is if anyone at the company knows the date at all.

That a member of staff who was in the know would then let the date slip - deliberately or not - to a national magazine seems doubly unlikely.

T3 does not specify exactly how this information was extracted, but any member of Phones4U staff that would potentially know the date is likely to have been media trained to the eyeballs. Shop floor staff would be fairly unlikely to know the launch date.

Also, Phones4U would undoubtedly realise the consequences of letting slip a date that Apple was trying to keep secret. So was the staffer who revealed the date guessing? Or perhaps repeating a rumour they had heard elsewhere?

The next-generation iPhone is not expected to be revealed until September, though traditionally iPhone updates are announced at the WorldWide Developer Conference (WWDC) held in June.