More than a quarter of stop and search records examined did not include sufficient grounds to justify the lawful use of the power, police watchdog Her Majesty's Inspectorate of Constabulary (HMIC) found in its first inspection of the power.
An inspection by the police watchdog into how forces in England and Wales use stop and search powers has found that the vast majority of them - 30 out of the 43 surveyed - had not developed an understanding of how to use the powers so that they are effective in preventing and detecting crime.
Only seven forces actually recorded whether or not the item searched was actually found, and half of forces did nothing to understand the impact the searches had on communities.
Officers spend an average of 300,000 hours conducting stop and searches, but on average only about 9% of the one million incidents recorded result in an arrest, a review has found.
Police are able to conduct stop and searches under 20 different powers, but the most common laws used are:
The Police and Criminal Evidence Act (PACE)
The Misuse of Drugs Act
The Criminal Justice and Public Order Act
The PACE act code of practice sets the standards intended to protect the public from the incorrect and unlawful use of these intrusive powers.
Under PACE forces are required to make arrangements for stop and searches to be scrutinised by the public, however the police watchdog found that less than half of all police forces in England and Wales comply with this.
Police officers are not adhering to the legal guidance on the power to stop and search, with the result that more than a quarter of searches conducted are "unlawful" according to a review by police watchdog Her Majesty's Inspectorate of Constabulary (HMIC).
HM Inspector of Constabulary Stephen Otter said:
Officers are not adhering to the guidance on too many occasions. It has slipped down the chief constables' agenda since the Stephen Lawrence Inquiry report.
The first inspection into the use of stop and search powers has found that police are using the power unlawfully in more than a quarter of instances.
After renewed concern about the way police use stop and search on the back of the 2011 riots, Home Secretary Theresa May ordered Her Majesty's Inspectorate of Constabulary (HMIC) to conduct its first ever inspection of the use of the powers in all 43 forces in England and Wales.