A coalition of businesses under the banner Face The Facts, Can The Tax is calling on the government to scrap the tax as the consultation on the levy comes to a close.
It believes the prospect of a minimum tax threshold for importers would permit some products to be imported tax free into the UK and "effectively incentivise rogue traders to purchase directly from other countries rather than buy taxed products manufactured in the UK".
The proposed levy on drinks such as Coca-Cola, Pepsi and Red Bull is central to the government's childhood obesity strategy and will come into force from 2018.
Drinks with 5g of sugar per 100ml will face a lower rate of tax while those with more than 8g per 100ml will face a higher rate, under plans unveiled by then Chancellor George Osborne as part of the Budget in March.
James Bielby of the Federation of Wholesale Distributors said: "The sugar tax will increase the number of imports brought into the UK.
"As the tax will not be collected at point of entry there is a massive opportunity for organised criminal gangs to exploit the tax and flood the market with imported product.
"Soft drinks in other countries often have higher sugar content so there will be a double whammy for the government - more sugary soft drinks could be available but no levy collected."
British Soft Drinks Association director general Gavin Partington said: "We know from the evidence around the world where they've tried a tax that it will not make a difference to levels of obesity."
