The new rules have been made under new European Union law called the Tobacco Products Directive.
Technically, the law came into force on 20 May last year, but companies were given a 12-month grace period to sell their old packs and bring in standardised packaging.
From next month, all tobacco must be packaged in drab, dark brown packs with no graphic branding.
The new packs are the same shape, size and colour, with two thirds of the front and back surfaces covered by pictorial health warnings, and written warnings on the sides.
From 21 May this year, anyone caught selling non-plain packs will face severe penalties.
Smokers will also no longer be able to buy smaller packs of cigarettes and rolling tobacco while menthols will be phased out completely by May 2020.
At the moment, rolling tobacco comes in 10g and 20g packets – but soon 30g will be the smallest size.
The ban includes some flavoured tobacco and cigarettes – including fruit, spice, herbs, alcohol, candy and vanilla.
There are also internal packaging requirements as well as rules for individual cigarette sticks. All other trademarks, logos, colour schemes and promotional images are prohibited.
Cost of cigarettes
A pack of cigarettes is now at least £8.81, which campaigners say is a key factor in making people quit smoking.
Action on Smoking and Health believe that removing the packet of ten cigarettes this means people will have to find that extra money for a packet.
“It will hit poorer and younger smokers harder who are more likely to buy smaller packs,” a spokesperson said.
Smokers’ rights group Forest said the new rules “treat adults like children and teenagers like idiots”.
New vaping laws will also come into force next month restricting sale of e-liquids and e-cigarettes.
Among the rules are: refillable tanks must have a capacity of no more than 2ml, e-liquids can not be sold in quantities greater than 10ml and e-liquid packaging must be child-resistant and tamper evident.