There has been a dramatic increase in the number of so-called 'head shops' operating around the country.

Gardaí say the businesses, which are legal, are selling herbal and synthetic substances and new premises are opening at a rate of one a week.

The Seanad has meanwhile passed an all-party motion urging the Government to introduce legislation to regulate the sale of dangerous substances through these shops.

The issue is to be the subject of a major debate in the Seanad next week.