A man has been arrested for allegedly trying to smuggle a drug out of the UK less than 24 hours after it was made illegal.

The 20-year-old is believed to be the first person in the country to be arrested for possession of qat, which has amphetamine-like qualities and became a class C drug at midnight on Tuesday.

The man's vehicle was searched during a routine stop check at the Channel Tunnel in Folkestone at 7.40am, Kent police said. He was held at the outbound tourist controls as he attempted to board the train for Calais, France.

Officers found what they believed to be about 1,102lb of qat, with a street value of at least £15,000, in pillowcases in the boot and back seat of his black Volkswagen. The pillowcases were taken away for analysis, police said.

A Kent police spokeswoman said: "The arrest is believed to be the first of its kind in the UK because qat was officially made a class C drug at midnight on June 24."

Qat, or catha edulis, is a flowering plant native to the Horn of Africa and the Arabian peninsula. It contains natural ingredients that are already controlled drugs both in the UK and internationally because they are harmful, according to the Home Office.

To help protect communities from the potential health and social harms associated with qat, and to ensure that the UK does not become a hub for international qat smuggling, it is now illegal to produce, possess, supply and import or export qat without a Home Office licence.

Anyone found illegally in possession of the drug could be issued with a warning or a £60 penalty notice by police, although repeat offenders will face arrest.

The Home Office has also said that anyone caught supplying qat or in possession with intent to supply, or those found importing qat, could face up to 14 years' imprisonment, an unlimited fine or both, if they are caught and prosecuted.

Qat, which makes its users feel more alert, happy and talkative when chewed, was made a class C drug, despite advice from the government's official advisers that it should not be classified.

About 2,560 tonnes of qat worth £13.8m was imported to the UK in 2011/12, bringing in £2.8m of tax revenues.

Drug experts and policy campaigners condemned the ban as it came into force. Danny Kushlick, director of Transform Drug Policy Foundation, said: "Yet again the government has ignored the advice of its experts and prohibited another drug. As ever, it will serve to create a new income stream for organised crime and that insurgents could profit from."

In a written statement earlier this year the home secretary, Theresa May, said that despite the recommendation of the Advisory Council on the Misuse of Drugs not to ban qat, the body acknowledged there was an absence of robust evidence in a number of areas.

Chief constable Andy Bliss, national policing lead for drugs, said: "Enforcement of the qat ban will be firm but proportionate."