Irish President Mary McAleese has signed into law an emergency plan guaranteeing Irish bank liabilities of 400 billion euros to shore up confidence in the country's financial system.
President McAleese formally signed the Credit Institutions (Financial Support) Bill 2008 on Thursday.
The legislation was announced by the government on Tuesday and approved early on Thursday by parliament after an all-night debate.
It has reportedly already triggered inflows of cash from Britain into Irish banks.
Ireland last week became the first euro zone country this year to officially go into recession.
The government announced last month it would bring forward its 2009 budget by two months to 14 October in a bid to restore confidence as public finances continued to deteriorate.