The Office for Tobacco Control has published findings that suggest 40% of retailers are continuing to flout the law by selling tobacco to children under 18.
The report finds that 63% of children were not prevented from buying cigarettes from vending machines is licensed premises.
The Office for Tobacco Control says retailers must meet their obligations under the law and refuse to sell cigarettes to people unless they present identification.
Chief Executive Éamonn Rossi warned retailers that complaints received will be investigated and regulations enforced.
He said serious penalties in the court system exist and his office would ensure offenders are penalised.
From next July tokens available from counters will be needed to purchase cigarettes from vending machines, it is anticipated that measure will lead to a reduction in illegal sales to children.
All point of sale advertising in shops will be abolished in July under new regulations that the OTC hopes will help reduce the number of young people smoking.
