A blanket ban on so-called "legal highs" will come into force at the end of the month, the Government has confirmed.
New laws passed to tackle the drugs, which have been linked to scores of deaths, will take effect around the country on May 26.
The legislation criminalises the production, distribution, sale and supply of psychoactive substances, with offenders facing up to seven years in prison.
It had been widely expected that the measures would be rolled out in April but the start date was pushed back with ministers saying they needed to "ensure the readiness of all the activity necessary to enable the smooth implementation".
Last week analysis by the Office for National Statistics said deaths linked to legal highs had more than tripled in two years.
The number increased over a 10-year period from 2004, with a total of 76 recorded during that time frame in England and Wales.
There was a "marked" rise between 2011 and 2013 when cases jumped from seven to 23.
Men in their 20s were found to be most at risk, while the average age for deaths involving the drugs is 28 - 10 years younger than the average for illegal drugs.
Plans to include poppers in the ban were abandoned after official advisers said the drug does not fall within the scope of the current definition of a psychoactive substance in the legislation.
The new Act states that a substance produces a psychoactive effect "if, by stimulating or depressing the person's central nervous system, it affects the person's mental functioning or emotional state".
A number of legitimate substances, such as food, alcohol, tobacco, nicotine, caffeine and medical products are excluded from the legislation.
Minister Karen Bradley said:"Psychoactive substances shatter lives and we owe it to all those who have lost loved ones to do everything we can to eradicate this abhorrent trade.
"This Act will bring to an end the open sale on our high streets of these potentially harmful drugs and deliver new powers for law enforcement to tackle this issue at every level in communities, at our borders, on UK websites and in our prisons.
"The message is clear – so-called 'legal highs' are not safe. This Act will ban their sale and ensure unscrupulous traders who profit from them face up to seven years in prison."