A dangerous type of ecstasy is being circulated in Brighton after the drug was smuggled into Britain.

Police intelligence services have warned Sussex officers after more than 125 of the white pills, marked with an "i", turned up at raves and clubs between May and August.

The drug is far more potent than normal ecstasy, has a hallucinogenic effect similar to LSD and is said to last up to four times longer.

The largest seizure of 65 tablets was at this summer's Glastonbury festival but batches have been found in Brighton.

Police in Wales, Bedfordshire and Edinburgh also made seizures of the drug.

Now an assessment of the dangers posed by the ecstasy-type substance, called 2C-i, has been issued to Sussex police by the National Criminal Intelligence Service (NCIS).

The substance, which is classified as a Class A drug in the UK, was first found in Britain this year and is believed to have come from continental Europe, possibly Denmark.

Standard ecstasy tablets have dropped in price to as little as £1 while dealers can get up to £10 for a 2C-i tablet.

An NCIS source said: "People who become involved in synthetic drugs risk their health simply because there is no regulation of how the drugs are manufactured.

"Users may not be aware of the side-effects of commonly-used ecstasy variants with potentially tragic consequences."

A police source said: "People who have taken 2C-i say it's very powerful. If someone unwittingly takes this drug to go clubbing and then starts hallucinating and thinking they can fly then obviously that could end badly."

A spokeswoman for drug experts Drugscope said: "With ecstasy there are so many different backyard manufacturers that people should be aware of what they are taking and tell other people.

"A lot of ecstasy-related deaths occur when people mix drugs, particularly with opiates and alcohol."