Guardian News and Media/London

The supplement that contributed to the death of the marathon runner Claire Squires is still available legally through overseas websites, it has emerged, despite it being banned for sale in the UK by regulators four months after she died.

Several websites outside Europe that ship to the UK still sell the “original” Jack3D supplement, containing the amphetamine-like stimulant DMAA (1.3 dimethylamylamine) that an inquest found on Wednesday had been a contributory factor in the death of the 30-year-old, one mile from the finish line of the London Marathon.

Because the Medicines and Healthcare products Regulatory Agency (MHRA) can only regulate products on sale on the UK high street or through UK-based websites, online retailers based overseas can still legally ship the product to the UK.

“We have no jurisdiction over other countries,” confirmed a spokesman for the MHRA, an executive agency of the department of health. “We try to work with regulatory partners to try to get websites taken down if they are in Europe but we can’t do much about sales from other countries like China, Russia or the US.

“Even if products are being sold into the UK from Europe, we only have a degree of success.” Once the product has entered the UK, it is not illegal to buy or possess it.

“Substances we have banned are not controlled substances,” added the MHRA spokesman.

“Our ruling means that products containing DMAA are, effectively, unlicensed medicines.”

He said there was a “vastly under-reported” problem of people selling banned products to each other in gyms. “This happens in a very ‘under the radar’-type way,” he added. “The majority of people who take DMAA products are regular gym-goers. The police would not get involved.”

The manufacturer of Jack3D reformulated the ingredients of the supplement after it was banned in the UK, the US, Canada and Australia but several sites still sell the original formulation.

When it banned the powdered supplement, the MHRA said it was the most popular of its kind in the UK. Squires took the supplement without realising that the powder contained DMAA and was unaware of the dangers.

The original formulation of the supplement was also available through a seller on the UK eBay site.

“The fact it’s banned now is very welcome. But the ban hasn’t eliminated the supply. The difference now might be that if you go looking for it you’re probably better informed than if you just pick it up off the shelf. This will hopefully alert people to the general risk that if you’re using something that has a genuine physiological effect, you should be careful,” said Graham Arthur, director of legal at UK Anti-Doping.