Leading internet sites have withdrawn potentially dangerous illegal tooth-whitening products from sale following an investigation.
Amazon, eBay and Google agreed to stop the goods being advertised on their pages after being alerted by consumer watchdog Which?
A European Union regulation adopted last year bans the sale of tooth-whitening products containing more than 0.1% hydrogen peroxide or chemicals which release hydrogen peroxide.
The limit was introduced in response to concerns that the chemical could damage teeth, lips or gums.
Stuart Johnston, from the British Dental Association, told Which?: "High doses of hydrogen peroxide can burn the lining of the mouth if it's not protected."
Peter Vicary-Smith, chief executive of Which?, said: "These products are illegal, but ineffective policing means they are still widely available.
"We have shared our findings with Trading Standards and will continue to urge online retailers to boycott such harmful products being sold in their marketplaces."
An eBay spokeswoman said: "We took action immediately and have built filters and appropriate structures into our system to address this issue.
"We do not allow unlawful products to be listed on our sites. If anything is brought to our attention we will investigate it and bring appropriate action."
A spokesman for Amazon said: "These items were offered by third-party sellers on our Amazon.co.uk Marketplace platform and have now been removed from sale.
"Please note that sellers on Amazon are prohibited from listing, on our Marketplace platform, products that do not comply with applicable laws."
A Google spokesman added: "We have a set of policies which govern what ads we do and do not allow... If we discover such ads we will take appropriate action."
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