White people are more likely to have drugs found on their person during stop and search, while black people are eight times more likely to be searched, new analysis suggests.
The disparity in delivery of the police stop and search initiative has been described as “troubling” by Her Majesty's Inspectorate of Constabulary and Fire & Rescue Services (HMICFRS), who carried out the analysis.
The “disproportionate” use of the power “continues to threaten trust and confidence in the police”, the watchdog added.
On its new data, the inspectorate said: "It suggests that the use of stop and search on black people might be based on weaker grounds for suspicion than its use on white people, particularly in respect of drugs.
"There may be a number of reasons for these findings but, taken alongside the fact that black people are more than eight times more likely than white people to be stopped and searched, they require an explanation that the service is currently unable to provide."
Stop and search is "one of the most intrusive powers available to the police", the HMICFRS said.
Police have powers under various laws to search people and vehicles without a warrant in specific situations.
Officers can stop and search people if they have "reasonable grounds" to suspect they are carrying items such as drugs, weapons or stolen property.
Some 153,750 stop and searches were carried out by Metropolitan Police officers in 2015 and last year.
The watchdog marked Scotland Yard as ‘good’ in relation to fairness and respect in dealing with stop and search.
It said: “The Metropolitan Police Service is good at treating all the people it serves with fairness and respect.”
But the report added: “The importance of treating people with fairness and respect is widely understood, although it does not always extend to less obvious situations, such as providing a poor level of service to the public.
“While the force provides training so that the workforce can recognise and overcome unconscious bias, the level of understanding of unconscious bias varies throughout the organisation.”
The Standard has approached Scotland Yard for comment.
The HMICFRS assessed more than 8,500 stop and search records - about 200 in each force in England and Wales.
A review of the "find rate" across the total sample was broadly similar across all ethnicities.
But when inspectors examined the subset of drugs searches, they found those involving black people were less likely to result in drugs being found compared with those involving white people or other ethnic groups.
For drug searches, the find rate was 33 per cent where the person searched was white and 26 per cent where they were black.
A similar pattern was seen where the suspicion was possession - 36 per cent white and 30 per cent black - and where the recorded grounds involved only the smell of cannabis - 37 per cent white and 29 per cent black.
Stop and search has repeatedly attracted controversy and reforms were introduced in 2014 by then home secretary Theresa May to ensure the tactic was used in a more targeted way.
Figures show this use of the powers has reduced sharply in recent years.
The number of stop and searches carried out by forces in England and Wales has fallen from more than a million a decade ago to just over 300,000 in 2016/17.
Although activity has fallen, the proportion of stops resulting in an arrest has reached a high of 17 per cent.
HMICFRS reviewed stop and search as part of its assessment of police "legitimacy", which looks at the extent to which forces treat people and their workforces with fairness and respect, and ensure their workforces act ethically and lawfully.
The watchdog said the results of this year's inspection were largely positive. One force was graded outstanding, 35 were good, while six were found to "require improvement".