An Bord Pleanála has refused a planning application for a €150 million terminal on the Corrib gas field in north Mayo.
Today's decision is likely to seriously delay the exploitation of the gas in the newly discovered Corrib Field.
The plan would have been the largest infrastrucural project in the west.
There had been strong local opposition to the project with farmers, fishermen, local residents and environmental groups all objecting to the plans.
An oral hearing on several specific planning aspects of the application ran for 22 days late last year, nearly two years after the first planning application was filed.
Royal Dutch Shell, now owner of Enterprise Energy Ireland (EEI), had been looking at a target date of 2005 or 2006 for piping the gas ashore.