The increase in demand for cannabidiol has doubled in the past year, it has been revealed.

According to the Cannabis Trades Association UK consumers of cannabidiol have surged from 125,000 to 250,000 in the past 12 months.

More and more consumers are relying on the controversial product which they claim cure's them of back pain, anxiety and epilepsy, among other health conditions.

As demand for the supplement has grown, Holland & Barrett, which has a large warehouse in Burton, has become the first high street retail store to sell the product.

The sale of Jacob Hooy's CBD+oil product (£19.99) has been so popular that sales have gone up by 37 per cent since hitting Holland & Barrett's shelves.

The high street store has revealed that due to the success in sales of the oil it will be adding four more products to the range, the Mirror reports.

Researchers are looking in to the health benefits of cannabis oil

A spokesman for Holland & Barrett said: "We have been surprised at the success and popularity of CBD oil since its launch.

"We are constantly looking to bring new and innovative ­products to market that help our customers.

"It is great to see in this instance that we can help with the demand."

CBD (cannabidiol) is an active substance found in hemp oil which is taken from the leaves and flowers of hemp.

It is legal as it has less than 0.2 per cent of the psychoactive tetrahydrocannabinol in it.

Holland & Barrett suggest that users put a few drops under the tongue two to three times a day, up to a maximum 15 drops per day.

It has a very "distinctive" taste, so customers are told to have a small drink of water afterwards to get rid of the taste.

Reviews of the product range from five star reviews which read: "Excellent for many many ailments, can't rate it highly enough. Liquid gold." to one star reviews which read: "I have been using for a few weeks. Not sure if I feel any benefit from using this product."

What is cannabidiol oil?

Cannabidiol is a thick substance which is made up of cannabinoids taken from the cannabis plant, specifically CBD and THC.

According to cureyourowncancer.org, it is the most potent of three main cannabis products, which are the actual cannabis flower (marijuana), resin (hashish), and oil (cannabidiol).

It has become a way to treat multiple types of cancer as well as diabetes and improve overall health.

Is it legal?

Well, it is still illegal to possess, supply or use cannabis oil but it is not illegal to possess CBD, or cannabidiol, which is one of the compounds found in marijuana.

CBD, unlike THC, is not psychoactive and therefore legal to possess and consume so don't expect to get high off some over-the-counter tablets.

CBD can be taken orally or applied specifically on the body and has been found to reduce anxiety and provide health benefits such as heart and brain health.

There have been a number of clinical trials evaluating the effectiveness of the substance saying that it has been effective on treating anxiety.

Worldwide Cancer Research have said that "there is nowhere near enough scientific evidence to back up" the fact that it cures cancer but there has been some "early laboratory studies which have given promising results."