The internet will hold so much digital data in five years that it will be possible to find out what an individual was doing at a specific time and place, an expert said yesterday.

Nigel Gilbert, a professor heading a Royal Academy of Engineering study into surveillance, said people would be able to sit down and type into Google "what was a particular individual doing at 2.30 yesterday and would get an answer".

The answer would come from a range of data, for instance video recordings or databanks which store readings from electronic chips. Such chips embedded in people's clothes could track their movements. He told a privacy conference the internet would be capable of holding huge amounts of data very cheaply and patterns of information could be extracted very quickly. "Everything can be recorded for ever," he said.

He was speaking at a conference at which a report commissioned by Richard Thomas, the privacy watchdog, was launched. Mr Thomas has said Britain is "waking up to a surveillance society that is all around us" and that such "pervasive" surveillance is likely to spread.

Sir Stephen Lander, the head of the Serious Organised Crime Agency (Soca) and former head of MI5, defended surveillance by the government.

"Significant intrusion into the privacy of a small minority is justified to protect the safety and well being of the majority," he said.