Northern Ireland could end up with cheaper cigarettes and tobacco than the rest of the UK as a consequence of a no-deal Brexit, a report has said.
ariffs would be applied by the UK to imports from the EU of cigarettes and tobacco in the event of a crash-out exit.
But Dr Rob Branston, an economist at the School of Management at the University of Bath, said Northern Ireland would avoid any rises.
The protocol means Northern Ireland will continue as part of the single market, subject to customs union rules and therefore avoiding tariffs.
Dr Branston co-authored the paper What Does Brexit Mean For UK Tobacco Control?
The report, which appeared in the International Journal of Drug Policy, said: "With 96% of UK tobacco products originating from the EU in recent years, a no-deal Brexit is likely to raise cigarette and tobacco prices.
"The Treasury has committed to apply new UK import tariffs on tobacco from January 1.
"If passed onto consumers, (this) would increase the average price of a typical 20-pack of cigarettes by around 30p and a 30g pouch of roll-your-own tobacco by £1.77.
"The benefits of Brexit-related flexibility will not extend to Northern Ireland, which will be considered part of the EU customs union, following EU rules and where imports to and from the EU will be tariff-free."
Asked if the differential could mean weekend visitors to Northern Ireland load up on tobacco products, Dr Branston said: "You could buy unlimited quantities for personal use and have your suitcase full. Whether you'd do that for 30p for a packet of 20, I don't know. But if it's a £1.77 saving on a brand of rolling tobacco, and that's the brand that you smoke, then that's quite a strong incentive."
Dr Branston said Brexit could also bring more flexibility in how tobacco is taxed in Britain, which could again widen the price gap with Northern Ireland if levies are increased.
A box of 20 Marlboro Gold cigarettes costs just over £12 in the UK, while a 30g bag of rolling tobacco costs around £16.
Ballymena newsagent Eugene Diamond said he hoped lower cigarette prices would help retailers.
"It could be an asset to retailers if we can offer a competitive price compared to people who smuggle cigarettes," he added.
"Smuggling is a big, big problem, and we have not only to contend with smuggled cigarettes from places like Russia, but with counterfeit cigarettes as well."
Dr Branston said Northern Ireland would also retain the EU's photograph health warnings on tobacco packaging, whereas the remainder of the UK will switch to using Australian imagery.
That is not because trading on World Trade Organisation terms after a no-deal Brexit is commonly referred to as "an Australia-type deal".
"It's simply because there are a small number of countries in the world which lead on tobacco control," explained Dr Branston.
"The UK happens to be one of those. So are Australia and New Zealand, for example.
"Given that you can't use European (images), you can try and create loads yourself, but it happens the Australian ones do what we want, so the UK has signed a deal to use those."