Around 80 post offices around the country closed for an hour at lunchtime today as staff protested over EU plans to allow competition in the postal sector.
Members of the An Post Group of Unions were took part in an EU-wide protest between 1pm and 2pm against the forthcoming liberalisation of the postal market.
Post offices operated by postmasters were not affected.
"An Post regrets the inconvenience caused to our customers as a result of this action," a company statement said.
Last October the EU Commission issued the first draft of the third postal directive which confirmed January 2009 as the date for full postal liberalisation across the EU.
An EU-wide umbrella group, UNI-Europa Postal, is calling for support of a petition opposing the liberalisation of the postal service.
Unions say the introduction of full competition has been disastrous for the universal service obligation where all parts of the country had to have the same level of deliveries and at the same price.