Personal information must be relevant, up-to-date and not excessive
Police may have to remove thousands of old criminal records of minor offences from the national database, after a ruling on holding personal details.
The Information Tribunal has dismissed appeals from five police forces who were ordered to delete old criminal convictions from the system.
It said personal information should not be kept for longer than necessary.
The five forces which appealed were Humberside, West Midlands, Northumbria, Staffordshire and Greater Manchester.
Police said the ruling could have "far-reaching implications".
Under current policy, criminal records remain on the police national computer for up to 100 years.
One of the cases involved at the tribunal was a record held by Humberside Police about the theft of a 99p packet of meat in 1984. The person involved, who was under 18 at the time, was fined £15.
Those concerned were caused harm and distress by the retention of this data
Mick Gorrill, information commissioner's office
Another, held by West Midlands Police, referred to a theft which took place more than 25 years ago, for which the individual was fined £25.
And a third, held by Staffordshire Police, related to someone under 14 who was cautioned for a minor assault.
The individuals complained to the information commissioner after the records showed up in checks when they went for jobs.
The tribunal upheld the ruling of the commissioner in November that the holding of the records did not comply with the Data Protection Act.
The act says personal information must be relevant, up-to-date, and not excessive.
The ruling could lead to thousands of people convicted of minor offences when young to apply to have their criminal record removed.
Mick Gorrill, ICO assistant commissioner, said the tribunal ruling was a "landmark" decision which would mean irrelevant details of old criminal convictions were deleted.
"Those concerned were caused harm and distress by the retention of this data," he said.
"These five cases - some of which date back nearly 30 years - relate to individuals who have been convicted or cautioned on one occasion and have not subsequently been convicted of any other offences."
But Ian Readhead, deputy chief constable of Hampshire and who leads on data protection for the Association of Chief Police Officers, said he was "disappointed" with the tribunal's decision.
"The Bichard Inquiry which followed the tragedy of the Soham murders recommended that forces should reconsider the way in which records are managed," he said.
"It is now important that clear national guidelines are put in place so that forces take a consistent approach to the retention of criminal records."
He said police chiefs would now discuss the ruling and decide what to do next.
In another ruling on the storage of information by the police, a government-appointed advisory body on Monday said police should be stopped from putting DNA samples from innocent volunteers on the national database.
The Ethics Group said samples obtained during police investigations should be destroyed at the end of an inquiry rather than loaded on to the national DNA database.