A growing black market for fuel smuggling is causing concern for police on both sides of the border.
Organised crime gangs are becoming increasingly involved in the illegal importation of fuel from eastern European countries, where petrol and diesel prices are much less than in Ireland and the UK.
Poland is currently one of the main sources of fuel for smugglers into the UK and Ireland.
The estimated price of diesel in Poland in the middle of March was €0.91, compared to €1.10 in Ireland and €1.30 in Britain.
Over the past year law enforcement agencies have noticed a shift away from the lucrative fuel laundering business due to the introduction of a new fuel marker that is believed to be impossible to remove.
However, early indications show this market is now being replaced by fuel smuggling.
Justice Minister David Ford warned the Assembly that the illegal importation of fuel was an emerging threat.
Mr Ford said that a six-month evaluation by HM Revenue and Customs of the new fuel marker, which was introduced into supplies in the UK and Ireland last April, pointed "to an overall shift away from illicit laundering".
"Whilst this is positive news, not least because of the negative impact which fuel laundering waste has on the environment, HMRC are now working together with colleagues from the Republic of Ireland to develop a strategy to reduce the current emerging threat, which is the smuggling of fuel," Mr Ford added.
Politicians, police and revenue officials on both sides of the border believe that dissident republicans are heavily engaged in fuel and other forms of smuggling.
HMRC officers are currently leading a major investigation into fuel smuggling in Northern Ireland and England.
Last month eight men were arrested, four in Northern Ireland and four in England, as part of the probe into a suspected fuel smuggling fraud worth £3m.
HMRC officers have seized 55,000 litres of fuel in an "ongoing" probe.
Chairman of Stormont's justice committee Alastair Ross said even though arrests were made last month there remained "a deep frustration that there are very few arrests or convictions in relation to fuel smuggling or fuel laundering".
"These activities not only hit legitimate retailers, but also cause environmental damage and often fund other criminal networks," the DUP MLA said.
"Last month I met with the National Crime Agency and encouraged them to work closely with both HMRC and local law enforcement to crack down on those who illegally produce or transport fuel."