More than 17,500 items were confiscated by officers after four stores were raided on the popular shopping street on Thursday night.
As part of Operation Jade, Trading Standards Officers seized goods including unsafe toys, counterfeit clothing and incorrectly labelled nicotine products.
Police confiscated two bags of foodstuffs that had more than the allowed legal limit of THC – the main psychoactive compound in cannabis – while other staff seized 4,000 items being sold by an unregistered food business operator.
Some 2,500 souvenirs were taken from unregistered businesses and illegal street traders.
Meanwhile, health and safety officers served three notices for unsafe electrical goods and poor standards of safety within premises.
Westminster City Council cabinet member for communities and regeneration, Heather Acton, said: “Oxford Street is the nation’s high street, our shoppers should be able to trust the products they are buying in the city are as described ‘on the tin’.
“The quantity and variety of goods seized by our officers is astonishing.
“Many of these goods are unsafe and certainly unhealthy.
“From cheap imitations of fashionable products to mislabelled tobacco and even psychoactive substances it’s vital that we protect customers and get these products off the shelves.
“This Christmas is make or break for many high street shops, and checking retailers will support legitimate businesses and protect the reputation of the West End as a leading destination for shoppers.”