The Information Commissioner's Office (ICO) has ruled out punitive action over BT and Phorm's secret advertising trials in 2006.
According to ZDNet, an ICO spokesperson said that after working with the two companies, it had ruled out any such measure at this stage.
The news follows the leak of official documents detailing the trials, which involved monitoring usage habits of 18,000 BT broadband customers as part of an ad-targeting campaign.
"We didn't have the internal [leaked] document, but Phorm and BT did present us with information [after the trial]. We've worked with BT and Phorm and we are not going to take any punitive action at this stage," the spokesperson said.
However, IT specialist Alexander Hanff, who leaked the document, insisted the tests had breached the Regulation of Investigatory Powers Act and the Data Protection Act.
Earlier this month, ZDNet reported Cambridge University computing expert Richard Clayton as suggesting that both companies should face legal action as a result of the trial.