A new law banning so-called legal highs will protect children and communities, according to home office minister Karen Bradley.

She said the new law would deliver a blanket ban on the sale and supply of new psychoactive substances, but would not criminalise users.

The class of drugs has been a headache for law enforcement and government because banning individual drugs has been ineffective, with new drugs emerging too fast for the law to catch up. In 2014, two new substances were detected every week.

Now the 2016 Psychoactive Substances Act has banned supplying, or offering to supply, a psychoactive substance and possession of psychoactive substance with intent to supply.

This has already resulted in the closure of dozens of "head shops" around the country which often supply legal highs as intended for other uses including bath salts and plant foods.

Karen Bradley said: "This doesn't replace or supersede the existing misuse of drugs act and other legislation. But it looks to restrict the supply and availability of these drugs on the high street.

"People think they are safe because they were deemed to be legal but they have not gone through testing processes and a blanket ban on their sale and supply is the responsible, proportionate thing for government to do."

"These drugs have been responsible for 400 deaths. Young people are turning up at A&E and doctors can't detect what they have taken and can't treat them. These substances are not safe and can lead to serious physical or mental disability and are in some cases fatal."

She denied there would be problems with enforcing the legislation and said Police Scotland and Scottish councils had been involved in discussions about the application of the new law. "Head shops have been closed down and the websites which used to openly sell these substances have now been criminalised. We have looked very carefully at the best way of doing this."