The Government has confirmed that the Russian Federation has so far made no payment for the cost of the large-scale clean-up operation, which was overseen by the Irish Coast Guard.
It is understood the Russian embassy in Dublin has disputed the size of the bill submitted by the Government in the belief that the size of the spill was much smaller than the coastguard has claimed.
The oil spill was identified by a satellite monitoring system on Feb 14, 2009, about 80km south of the Fastnet Rock.
A short time later, an Air Corps aircraft spotted the slick in the vicinity of the Russian aircraft carrier, Admiral Kuznetsov, which was being refuelled at the time in the company of a tanker and a tug.
At one stage, the spill covered an area of about 50sq km.
It is estimated that about 300 tonnes of oil leaked into the sea during the incident Fortunately, the prevailing weather conditions over subsequently days allowed the oil slick to disperse off-shore with no major environmental damage to the Irish coastline.
However, the Irish Coast Guard expressed concern at the time that notification of the pollution had not been made earlier.
A Russian military delegation which travelled to Ireland after the incident expressed regret for the leak and claimed it may have occurred when bilges were inadvertently pumped out of the 46,000-tonne vessel. An internal investigation revealed the spill was due to “technical malfunction and human error”.
Transport Minister Leo Varadkar confirmed in a written reply to Labour TD Kevin Humphreys last week that the Russian navy had accepted responsibility for the oil spill.
While Mr Varadkar acknowledged there was no legal mechanism to compel the Russian government to pay for the clean-up, he said the Department of Foreign Affairs submitted a request for payment to the Embassy of the Russian Federation almost three years ago.
The embassy was provided with a bill for a total of €155,166, despite initial estimates that the cost could be up to €250,000.
It is unclear how proactive the Department of Foreign Affairs has been in putting pressure on the Russian government for payment of the clean-up bill. However, it is understood there have been ongoing discussions between the parties over the past few years.
Neither the Department of Foreign Affairs nor the Russian embassy could provide a spokesperson for comment when contacted.