The fall-out from the T-Mobile customer data breach reported this week is likely to lead to future jail sentences for those involved in the illegal sale of personal details.

T-Mobile has admitted some of its employees were involved in the sale of customer details to outside agents involved in trying to win new customers for rival operators.

Under current law, the maximum sanction for breaching the Data Protection Act (DPA) in this way is a £5,000 fine for those responsible. The government and the Information Commissioner's Office (ICO) are now calling for prison sentences for those found to be selling personal details illegally.

Before T-Mobile publically admitted the data breach, it was already privately working on an investigation into the scandal with the Information Commissioner. T-Mobile confirmed it was the subject of the investigation after all the other rival mobile operators said they weren't involved, after the Information Commissioner publicly said he was working on the case without naming the actual operator involved.

The threat of custodial sentences from 1 April 2010, for breaching section 55 of the Data Protection Act, follows a recently started government/ICO consultation into increasing the maximum fine to £500,000 for firms that are responsible for "serious" data breaches.

Information Commissioner Christopher Graham said, "I am keen to close down the entire unlawful industry in personal data. But we will only be able to do this if 'blaggers' and others who trade in personal data face the threat of a prison sentence."

In another case being investigated by the ICO, blaggers - data thieves pretending to be someone else - are said to have used forged identity documents to gain unlawful access to 41 people’s credit files held by a credit reference agency.

Whilst the other mobile operators currently not being investigated in the T-Mobile data breach may think they have avoided a media storm, by coming forward and saying they are not involved, the public may take a dim view of the fact the stolen T-Mobile customer data was being used to win them new customers.