Ferry fares for residents on the largest of the Aran Islands are set to increase by almost 90%.
The cost of a return journey for residents travelling from Inis Mór to the mainland will go from €8 to €15, after the Department of Arts, Heritage and the Gaeltacht failed to secure any tenders for a public service contract on the route.
The existing operator, Island Ferries, had sought an increase in the annual subvention it received for running a twice daily service.
The company said the subsidy on offer did not make it viable for it to operate the contract.
Island Ferries founder Paddy O'Brien said increased fuel costs mean he has no option but to increase fares from tomorrow.
The company will continue to run PSO services to Inis Oírr and Inis Meáin.
The cost of a return journey to the mainland for inhabitants of those islands is increasing from €8 to €10.
The Department said efforts have been made to negotiate an agreed solution but that it could not provide a 300% increase in the annual subvention to provide a service to Inis Mór.
Manager of the Inis Mór co-operative, Cathy Ní Ghoill, said it is unacceptable that the State's most populated island no longer has a guaranteed ferry service.
She said islanders are worried that the service could be withdrawn in future if it was deemed to be not commercially viable.