Derbyshire police have welcomed a new law banning 'legal highs'.
The Psychoactive Substances Act - which came into force at midnight - prohibits 'any substance intended for human consumption that is capable of producing a psychoactive effect'.
Under the new legislation, dealers will face up to seven years in prison and people found in possession of 'legal highs' could be jailed for up to two years - the same as a custodial penalty for possession of a class C drug. In addition, police will be handed new powers to search for and seize and destroy the substances.
Superintendent Kem Mehmet, of Derbyshire police, said: "We welcome this act as it provides us with some clarity and gives us the powers to tackle the supply of psychoactive substances.
"The Psychoactive Substances Act provides a blanket ban on the production, supply and importation of new psychoactive substances. This legislation will fundamentally change the way we tackle such substances.
"Members of the public have become frustrated by our lack of ability to close down shops that openly sell these products, which are the cause of a lot of anti-social and irrational behaviour and violence.
"We will now visit all shops that previously sold these substances to ensure that they are aware of the change in the law and to seize any stock that they have left.
"We would ask members of the public to tell us about any shops or people who continue to sell them.
"We will also be actively using the powers given to us to search people and seize substances.
"Our message to users remains the same - you never know what you are taking. Even if these substances are packaged and named as a brand you have seen before there is no guarantee the chemicals are the same."
'Legal highs' produce similar effects to illegal drugs like cocaine, ecstasy and cannabis.
The Government said they were linked to the deaths of at least 140 people in the UK in 2014.
But the Office for National Statistics found that in 60 per cent of the fatalities connected to 'legal highs' between 2004 and 2013, the deceased had also ingested other substances.
The ban has been welcomed by many individuals, organisations and charities - but Dr Adam Winstock, a consultant addiction psychiatrist and founder of the Global Drug Survey, criticised the legislation.
He claimed the law will 'likely push people back towards illegal drugs'.