T-Mobile UK has taken against Skype and other VoIP applications - at least as far as its new Web 'n' Walk Professional mobile internet access airtime package goes. According to the company's service terms and conditions, it's none too keen on instant messaging either.

A quick read of the carrier's Web 'n' Walk Professional webpage reveals that "use of Voice over Internet Protocol and Messaging over Internet Protocol [over the service] is prohibited by T-Mobile. If use of either or both of these services is detected, T-Mobile may terminate all contracts with the customer and disconnect any SIM cards and/or Web ‘n’ Walk cards from the T-Mobile network".

Since the Web 'n' Walk Professional is, as we reported earlier today, based on 3G access via a notebook data card which will, once the service is up and running this coming summer, also support the HSDPA 3G speed boost technology, we can only presume T-Mobile is anxious to protect its voice revenue, or is worried that users will inadvertently surpass the 2GB data transfer limit the cellco applies to the package. Certainly, the technology and tarriff would otherise appeal to Skype users keen to make cut-price calls on the move.

We've already reported how the package is touted as forcing "no data download limits" on users even though the company applies... er... a 2GB monthly data transfer maximum. T-Mobile describes this not as a limit but as a "fair use policy", implying that punters requiring more are somehow out to get more than their fair share.

If they try and use more than 2GB, they run the risk that "if usage is not reduced, notice may be given, after which network protection controls may be applied which will result in a reduced speed of transmission," the carrier warns.

T-Mobile UK's website say the company applies the limit to "ensure a high quality of service for all our customers" - even, presumably, those who use a lot less than 2GB.

We asked the company to comment further this morning, and we're still waiting to hear from it. ®