Senior Garda sources say the gang intended to distribute some of the cocaine here and supply the rest throughout Britain and Europe for the Christmas market.
The seizure comes less than three months after the Naval Service intercepted the motorised yacht Makayabella 300 miles off the south-west coast of Ireland. She was carrying cocaine worth €82m.
Gardaí believe the cocaine seized in Portsmouth on Monday came from the same supply chain in Colombia as the drugs found onboard the Makayabella.
Gardaí said the seizure would be a major blow “to elements of an Irish organised crime gang”.
Criminal gangs here are clubbing together to purchase large amounts of cocaine from Colombian drugs lords and are working with a network of British and European counterparts to distribute the Class A drug.
The British National Crime Agency (NCA) found 300kg of cocaine concealed in the Star Stratos when they searched her in Portsmouth on Monday.
The cocaine was concealed within a shipment of bananas which originated in Colombia.
The NCA said the operation was carried out in cooperation with the gardaí and that investigations are ongoing.
NCA deputy director Tom Dowdall said they were working with law-enforcement partners in the Britain and Ireland and had prevented what was likely to be “very high purity cocaine” reaching the streets.
“Our investigations into the organised crime groups likely to be responsible for this shipment continues,” Mr Dowdall said.
The NCA reiterated that it was the second successful operation in recent months in which it had cooperated with An Garda Síochána to smash drugs supplies into western Europe.
Meanwhile, Customs officers have seized counterfeit Nike runners, worth nearly €300,000, which were being smuggled into this country for the Christmas market. A Customs source said that 2,000 pairs of runners were discovered during a routine profiling operation at Tivoli docks, Cork and could have netted the smugglers €292,000.
The runners were discovered in a shipping container which had originated in China and Customs sources said the Nike ‘Shox’ brand footwear would have looked authentic on first inspection. Fake logos were stitched onto the shoes and fake logos were also printed on the boxes they were in.
A Revenue spokesperson said the merchandise is believed to have been intended for the “lucrative” Christmas market.
Gardaí are also keeping an eye open on outlets in the Cork in the run-up to Christmas. In January they seized €1.5m worth of counterfeit Ugg boots from a warehouse on the northside of Cork City. They also seized hundreds of thousands of euro worth of counterfeit shoes, handbags, and clothes in Midleton.