Junior Defence Minister Paul Kehoe has secured Government approval to purchase another ship for the Naval Service.
This ensures that the service will continue to have at least eight ships while at the same time replacing older vessels.
Mr Kehoe told the Irish Independent last night that the Government had agreed to provide €54.3m ( €66.8m after Vat) the purchase an additional ship after reaching a contract agreement with Babcock International to build it at their headquarters in Appledore, Devon.
He said: "This is a major benefit to the State and will be a further significant enhancement of defence capability.
"The acquisition of a fourth sister ship of the same class as those recently commissioned will secure crewing, training, logistical and maintenance advantages", he added.
The new ship will be delivered within two years and its purchase is in line with the maritime capability requirements set out in the government white paper on defence last year.
At the moment, the Naval Service has eight ships but the LE Aisling will be decommissioned next week.
It will be replaced by the LE William Butler Yeats, which comes on stream next month.
Following an open tender competition, a contract was placed in 2010 with Babcock International for the provision of two new offshore patrol vessels, with an option for a third.
The first, LE Samuel Beckett was handed over at the end of April 2014, while the LE James Joyce was delivered in July last year.
The LE William Butler Yeats is the third and it will be delivered in July after the completion of sea acceptance trials.
The value of the original contract, including the third ship, is €199.4m, including Vat.
Mr Kehoe, inset, who is minister of state with special responsibility for defence, said the Government was proud of the contribution the Defence Forces made to the State's security.