The operators of four million closed circuit television (CCTV) cameras were told last night to destroy images of people caught on film as soon as possible.
The instruction from Richard Thomas, the Information Commissioner, followed the disclosure in The Independent on Monday that Britain is now the most-monitored nation in the world.
Mr Thomas said he was not stipulating firm limits on the length of time CCTV operators held on to pictures of the public but he suggested a month might be a reasonable period for images from city and town centre cameras to be retained. It could be longer for cameras at cash-machines given that evidence of fraud can take many weeks to emerge.
On the other hand, pictures taken in pubs and clubs to combat violence could be destroyed within days.
Mr Thomas said: "As long as they have got a legitimate reason for holding it for x days or months, that is fine. They have got to think it through. Just holding it for 10 years for the sake of it is not acceptable."
He added: "If they were simply keeping information for no clear reason, then I think we would have quite strong concerns."
Mr Thomas said he shared worries about the expansion of CCTV cameras and spoke out in defence of the much-maligned Data Protection Act, which has faced damaging headlines in recent weeks.Reuse content