A letter will be sent to the Revenue Commissioners from Labour Party offices this week demanding an explanation for the relaxing of security in Shannon Airport since 2004.
Labour Party TD for Limerick East, Jan O'Sullivan, will raise concerns over the restructuring of rosters for customs officials that leaves up to 17 flights per week unchecked by customs on arrival at the airport.
Of those, 14 originate in the US, two arrive from London Heathrow and one from North Africa.
The figures have raised serious concerns over the potential for drug trafficking or even terrorist attacks, given the amount of US troops still passing through the airport.
Green Party TD John Gormley expressed his concern to ireland.comover the possibility of Shannon, in particular, being a terrorist target.
"God forbid if any part of Ireland was a terrorist target but I would be surprised if the security forces here didn't see that as possible," said Mr Gormley.
"US troops - who are seen as the enemy - use it and their Commander-in-Chief, George W Bush has landed there."
Concerns were raised after an answer provided by Minister for Finance Brian Cowen to a Parliamentary Question on Cork Airport posed by Labour Counsellor Ciaran Lynch earlier in the week.
Customs officers operate under the auspices of the Revenue Commissioners, which is answerable to the Department of Finance.
Mr Cowen confirmed that neither Shannon or Cork International Airports had customs staff rostered on a 24-hour basis.
Mr Cowen said: "Overall, the majority of Shannon flights outside rostered hours were attended and checked in 2005."
Ms O'Sullivan however, has described this reassurance as "vague" and "not good enough", adding that the only solution is to "have someone there all the time."
A Customs spokesman confirmed Mr Cowen's numbers to ireland.com, but like the minister, stressed that officers are present for flights that were considered a general risk or when specific intelligence was received relating to passengers or flights.
"We apply our resources in accordance to the risk and we have a 24-hour, on-call service to meet any flights we consider a risk," the spokesman said.
Despite the assurances however, many are not convinced.
Refereeing to the situation in Cork, Mr Lynch said: "This is a major concern and with such staffing coverage it would be easy for a drug trafficker to slip through the airport into the country unnoticed.
"We see where the level of cocaine being imported through our airports has risen significantly in recent years. There were 1,100 drug seizures in our airports last year, compared to just 361 in 2001, so the level of drug trafficking is clearly increasing.
"It's unacceptable that Brian Cowen is still allowing this situation to continue on a day to day basis. I'm calling on him to sort this problem out immediately," added Mr Lynch.