The police's powers of arrest will be dramatically boosted from this Sunday.
New laws which make all offences arrestable come into force, marking a major departure from the traditional patchwork of arrestable and non-arrestable offences in England and Wales.
At present, officers can generally arrest a member of the public if they suspect them of committing an offence which carries at least five years' imprisonment.
However, the situation is made more complicated by a number of exemptions which have been introduced in recent years.
Current non-arrestable offences include impersonating a police officer, failing to stop a vehicle when ordered to do so, manufacturing or selling an offensive weapon, failing to
hand over a passport to a court and unauthorised access or modification of computer material, which deals with some more minor hacking offences.
Under the new rules, officers will have to apply a "necessity test" which sets out the criteria for whether it is necessary to arrest someone.
A new code for officers says they should "consider if the necessary objectives can be met by other, less intrusive means".
It adds: "Arrest must never be used simply because it can be used.
"Absence of justification for exercising the powers of arrest may lead to challenges should the case proceed to court. When the power of arrest is exercised it is essential that it is exercised in a non-discriminatory and proportionate manner."
Home Office Minister Hazel Blears said: "The introduction of a single rationalised power of arrest simplifies arrest powers and requires the police officer to consider the 'necessity' of the arrest.
"This means that the officer has to focus on the individual circumstances of the case and the needs of the investigation."
Originally proposed in August last year by former Home Secretary David Blunkett, the change is contained in the Serious Organised
Crime and Police Act 2005. Ms Blears said: "It is vital that the police are equipped with the powers they need to enable them to do their jobs properly and effectively.
"The powers need to be updated in order to reflect modern policing priorities and the changing nature of criminal activity."