...were already conducting in-depth investigations, so it would not have been a sensible use of ICO resource to do the same."
The information commissioner is now calling for Google to delete the data as soon as it can legally do so. In an apology issued on Wednesday, the company said it is working towards this deletion.
"We are profoundly sorry for mistakenly collecting payload data in the UK from unencrypted wireless networks," said Peter Fleischer, Google's global privacy counsel, in a statement. "We are in the process of confirming that there are no outstanding legal obligations upon us to retain the data, and will then ensure that it is quickly and safely deleted."
Those legal obligations include organisations or proceedings that could compel Google to keep the details, the company told ZDNet UK.
Privacy campaigners responded to the ruling by criticising how the ICO had handled the situation.
"The greatest example of mismanagement of data has come from the ICO, not Google," Privacy International director Simon Davies said. "[The investigation] really was a farce."
For example, the decision in July that Google had not gathered significant details directly contradicted the findings of the French privacy authorities in June, according to Privacy International. However, the ICO responded that, as far as it is aware, only Canada has published a detailed report after an in-depth investigation into the matter.
Privacy International also said it had confirmation from the ICO that its staff who examined the data did not have any technical training. Asked by ZDNet UK whether the staff included people with IT training, the ICO responded that they were "long-standing data protection experts".