Slimmers have been warned to destroy medicines bought online that contain illegal ingredients.
The Irish Medicines Board (IMB) revealed there has been a 600% increase in the number of slimming products seized in recent years that contain the substance Sibutramine.
The drug has been withdrawn across Europe and around the world due to the increased risk of heart attacks and strokes.
The IMB has issued a list of 38 online slimming products which still contain Sibutramine - some which fraudulently do not declare it among ingredients on the pack.
It advised customers to stop taking them immediately and seek medical advice with any concerns.
John Lynch, director of compliance at the IMB, said: "We are identifying Sibutramine containing products that, in some cases, are labelled as containing only natural ingredients.
"In addition, the packaging is often quite sophisticated and is intended to convince purchasers they are buying legal and safe products.
"The products are often presented as natural slimming aids but many do not refer to Sibutramine in their packaging and are deliberately misleading consumers.
"Medicines containing Sibutramine have been removed from the worldwide market due to safety concerns."
The list of illegal Sibutramine containing products include Botanical Slimming 100% Natural Soft Gel (Capsules), which is also sold as Meizitang, Lipro Diet Pills, and Slimforte Slimming Coffee and Capsules.