Police hope educating the public about the smell of cannabis will make it easier to clampdown on those growing the drug.
Hundreds of police officers have failed new fitness tests which are due to become mandatory later this year, official figures show.
In a damning report, the HMIC said police are failing victims of domestic violence right across England and Wales. Urgent reform is needed.
The Home Secretary has hit out at the police after a series of inspections showed officers may be failing to report as many as one in five crimes.
Theresa May said the inspection from Her Majesty's Inspectorate of Constabulary showed "unacceptable failings by the police".
She warned that the police could now start recording more offences, leading to a spike in headline crime statistics, but she insisted this did not mean crime was going up.
"It is quite possible, once HMIC has completed its work on recorded crime statistics and made recommendations on how the police need to improve, that we will see an increase in recorded crime," she said in a statement.
"If that increase is driven by improved accuracy in the recording of crime or more victims reporting crime to the police, we should welcome it. Such an increase would not mean that crime itself is rising," she added.
As many as one in five crimes could be going unrecorded by police, a major report has found.
An investigation by Her Majesty's Inspectorate of Constabulary (HMIC) also found some offenders were being issued with 'out-of-court disposals' such as a caution rather than being prosecuted.
Inspectors looked at 13 different forces and said they could not rule out "discreditable or unethical behaviour" from officers for the failure to record some crimes.
Theresa May has said controversial police powers to stop and search are to be revised.
The Home Secretary wants to cut misuse of the powers, which may have been used illegally a quarter of a million times last year.
ITV News UK Editor Lucy Manning reports.
The Home Secretary told the House of Commons she had "long been concerned about the use of stop and search".
Theresa May said: "While it is undoubtedly an important police power, when it is misused stop and search can be counter-productive
"First, it can be an enormous waste of police time. Second, when innocent people are stopped and searched for no good reason, it is hugely damaging to the relationship between the police and the public. In those circumstances it is an unacceptable affront to justice."
Police will face disciplinary action if they fail to stick to a revamped code of practice for using controversial stop and search powers, the Home Secretary has told the House of Commons.
Theresa May told MPs that fresh legislation on stop and search will only be introduced if forces fail to comply with the new guidance. She said officers will need to pass a rigorous new assessment of how stop and search powers are used.
If they do not pass the test they will be stripped of being able to use the powers. Her Majesty's Inspectorate of Constabulary (HMIC) found 27% of stop and searches examined by the watchdog did not contain reasonable grounds for suspicion.
The mother of Azelle Rodney, who was shot dead by a police marksman nine years ago, has criticised the Crown Prosecution Service for the "intolerable" delay in making a decision on criminal charges.
Susan Alexander has written to the CPS telling them that "no mother should have to go through this".
Mr Rodney was shot six times when officers stopped a car he was travelling in with two other men in Edgware, north London.
The officer who fired the fatal shots, known only as 'E7', lost an appeal against a public inquiry finding that he had used excessive force when he shot Mr Rodney.
His lawyers argued that the police had intelligence that the men in the car were carrying machine guns and that the officer had fired because he thought Mr Rodney was about to shoot him.
The Crown Prosecution Service has charged a police officer with distributing illegal images on his phone. In a statement, Deputy Chief Crown Prosecutor Jenny Hopkins said:
We have been asked to review a file of evidence submitted by the Metropolitan Police Service’s Department of Professional Standards concerning alleged offences under the Obscene Publications Act. Following a review of the evidence, we have concluded that James Addison, a police constable in the Diplomatic Protection Group, should be charged with 11 offences.
It is alleged that between 17 February 2013 and 6 June 2013, PC Addison distributed moving images via his mobile telephone, contrary to section 2(1) of the Obscene Publications Act 1959.
Public confidence in the police has been "severely shaken" by a series of controversies, an annual report into the service has said.
Her Majesty's Chief Inspector of Constabulary. Tom Winsor, said cases such as the Stephen Lawrence investigation and the 'plebgate' scandal involving former Chief Whip Andrew Mitchell had all damaged the police's reputation.
"Controversies and revelations of a serious and negative nature in relation to the conduct of some police officers, both past and present, have hurt public confidence in the police," his report says.
The future success of the police is dependent on attracting the best and brightest to careers in the force, the Policing Minister has said, as a move to fast-track officers into senior roles come into force.
Damian Green added: "This is the first time that chief constables will be able to recruit talented and motivated leaders from other walks of life, who can bring a wide range of experience and expertise.
"They will receive world class training from the College of Policing and will bring a fresh perspective and approach, opening up policing culture which will benefit their colleagues and the public."
Police forces should reflect the communities which they serve, the Prime Minister said, as a move to fast-track officers into senior roles come into force. David Cameron said:
Schemes like these will enable talented and experienced people from a range of backgrounds to bring new ideas and a fresh approach to policing.
We have already slashed red tape and cut bureaucratic targets, this is about opening up policing culture by making the workforce more diverse. I want to see all forces in England and Wales rolling out these schemes.