A record amount of almost 44,500 cigarettes were found, worth over £20,000.
Oxfordshire County Council's trading standards officers have made their biggest seizure of illicit cigarettes and hand-rolling tobacco yet.
This follows an operation with Thames Valley Police in Banbury on Friday, when a terrace house was raided.
It resulted in the record haul of 44,440 cigarettes and 24,500 grams of hand-rolling tobacco, with an illegal market value of over £20,000.
A man, 40, and woman, 39, were both interviewed under caution at Banbury Police Station. The investigation is ongoing.
The sting took place under Operation CeCe, a national trading standards initiative in partnership with HRMC which is playing a significant role in disrupting the illicit trade and helping to take illegal tobacco products off the streets.
Jody Kerman, Oxfordshire County Council's Head of Trading Standards, said: "While we are confident that Oxfordshire is well on its way to being free of illegal tobacco in shops, we know that illicit tobacco is still being sold across the county in different ways. One of those ways is from 'stash houses'.
"If you're living on a street where customers are regularly turning up to a property and leaving shortly afterwards, usually with a plastic bag containing the tell-tale rectangular shape box of 200 cigarettes, report it to us in the strictest confidence".
Reports can be made anonymously by calling 0300 999 6 999 or visit stop-illegal-tobacco.co.uk