SIPTU has called on Minister for Transport Eamon Ryan to turn away a tanker carrying oil from Russia which is due to dock in Dublin Port tomorrow night.
SIPTU has also written to the Chief Executive of Dublin Port, Eamonn O'Reilly, with the same request.
In a statement, SIPTU Divisional Organiser Karan O’Loughlin said: "Given the unfolding horror in Ukraine as the invasion by Russian forces aggressively proceeds, our members and other workers who are expected to unload this vessel are angry and upset at being put in this position."
The statement goes on to say "...Workers should not be expected to carry the weight of circumstances such as these and are urgently calling on the Government and the Dublin Port company to ensure the STI Clapham is prevented from landing its Russian oil cargo in Ireland."
RTÉ News first reported last week that a consignment of Russian oil, understood to be diesel, was on its way to Dublin Port from the Russian Baltic port of Vysotsk.
It left there on 3 March and stopped at the port of South Stifford on the southeastern coast of England on Wednesday.
The ship carrying the consignment is the STI Clapham, registered in the Marshall Islands.
It is currently on its way to Dublin and is expected to dock tomorrow night.
The Department of Transport has said it is aware of the particular consignment on its way to Dublin Port via the United Kingdom.
It said the Government is ensuring that EU sanctions already agreed are being implemented, including in the transport sector.
"The effectiveness of EU sanctions is evident, and discussions continue with EU partners on further measures.
"As matters currently stand, the European sanctions applying to Russia exclude oil product. Petrol, diesel, home heating oil and kerosene are not subject to sanctions and there would not be any legal basis to refuse to accept such products," the Department said.
Fuels for Ireland CEO Kevin McPartlan said the purpose of sanctions was to avoid giving finance to Russia.
However he said the fuel on the ship has already been paid for, so if it is turned around it will do nothing to damage the Russian economy or the company it was bought from.
He added that we do need to ensure that we have sufficient supply coming into the country and the stock on that boat is likely to give us three days national supply of diesel.
"We can't afford to turn that around if we want security of supply," he said.
Additional reporting by Will Goodbody