Police officers should not routinely stop and search someone simply because they smell cannabis, according to official guidance.

While being caught in possession of the Class B drug can result in a five year prison sentence, police are being advised to walk away even if they strongly suspect someone may have been using the substance.

The official guidance was issued by the College of Policing, which helps formulate the training for all officers in England and Wales.

But last night one of the country's most senior policemen described the guidance as "wrong" and said he would still encourage his officers to carry out stop and search on cannabis suspects.

Chief Constable Andy Cooke of Merseyside Police, wrote on Twitter: "The guidance in my view is wrong and the law does not preclude it .

“Smell of cannabis is sufficient to stop search and I will continue to encourage my officers to use it particularly on those criminals who are engaged in serious and organised crime."