A surge in the number of homeless people using a new drug said to have withdrawal effects more severe than heroin and crack cocaine has been reported in Westminster .

Spice, one of the street names given to synthetic cannabis, can cause severe psychotic episodes in users, who experience distressing hallucinations, vomiting and seizures.

Latest figures show 22% of the 430 people staying in Westminster hostels in the first four months of 2016 were using the drug, despite the drug being relatively unknown just two years ago.

The sudden rise in its use has prompted the city council and homeless services to speak of the dangers of the drug.

Ewa Kapica, an outreach worker at Westminster-based homelessness charity The Connection at St Martins-in-the-Fields, said: “I’ve witnessed people thrashing around on the floor, experiencing vivid hallucinations, screaming they want to ‘end it all’.

"These fits are followed by crashes; the person becomes unresponsive and the emergency services step in. It’s terrifying.

“One user was convinced he had a worm climbing through his blood stream and nearly rolled into traffic before an ambulance and two police units arrived.”

Spice users also often exhibit aggressive or non-responsive behaviour, which has seen a rise in reports of abuse from homeless services staff, and prevents rough sleepers from engaging with the health, housing, education and employment services the council and its partners offer.

Councillor Nickie Aiken, cabinet member for public protection at Westminster, said: “Spice is cheap, readily available and highly addictive, so it’s little wonder our support services are seeing an increase in the number of users. In just two years a new drug epidemic has taken over the streets of London.”

And she is calling on groups to come together to tackle the problem: “It is devastating to see rough sleepers unable to move forward with their lives because of an addiction.

“That is why I am calling on central government, homelessness charities and health partners to come together and develop a long-term solution to a drug that continues to strengthen its grip on some of the most vulnerable people in society”

Watch a gang use a helicopter to smuggle drugs into the country

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A new Psychoactive Substances Act came into effect this year , making it an offence to produce or supply former "legal highs" such as spice. But Cllr Aiken said more is required: “We need legislation to go even further, giving the police more powers to confiscate drugs from users as well as dealers, to be truly effective.

“Everyone has a part to play. We don’t want to tell people what to do, but all evidence shows that giving directly to someone on the street does not support them into accommodation, but is more likely to sustain a drug habit.”

If you are concerned about a rough sleeper:

* Contact StreetLink via streelink.org.uk or call 0300 500 0914. They will make sure local teams are alerted and you can get an update on what happens to them.

* Text REALCHANGE plus the amount you wish to give (£1, £2, £3, £4, £5 or £10) to 70500. 100% of your donation will be split between three local homelessness charities.