Watch: What Are Legal Highs?

A blanket ban on legal highs due to come into force in the U.K. this week will lead to more deaths and only benefit drug dealers and politicians, critics have claimed.

The substances, which mimic the effects of already banned drugs, are being outlawed on Thursday due to concerns their potency is fueling health problems and anti-social behavior.

But critics have said that the law will simply force users, who are often among the most vulnerable in society, to turn to street dealers and the criminal underworld, leading to more drug-related deaths.

Daily Emails and Alerts - Get the best of Newsweek delivered to your inbox

But what are legal highs?