Ryanair boss Michael O'Leary urged Irish voters to back the EU Lisbon Treaty in a second referendum, warning a second "No" vote would lead to Ireland's economy being "destroyed".

Mr O'Leary said it was "vital" for Ireland to back the Treaty in the October 2 poll, stressing that membership of the EU and Europe's euro single currency had transformed the economy and the lives of millions of Irish people.

In a referendum in June last year Ireland - which is constitutionally bound to put the Treaty to a public vote - sent shockwaves through the EU when it rejected the treaty by 53.4 per cent.

"Ireland must vote 'Yes to Europe' on October 2; otherwise our economic future will be destroyed by government and civil service mismanagement and the narrow vested interests of the public sector trade unions," he said.

Without the EU, Ireland's economy would be run by "incompetent politicians", an "inept civil service" and "greedy public sector trade union bosses", said the boss of Europe's biggest budget airline.

He described opponents of the Treaty as a "ragbag amalgam", and said Ryanair would spend more than €500,000 campaigning for a "yes" vote.