The performance of An Post has slipped by five percentage points in one year, according to a survey released by regulator ComReg.
Only 73 per cent of standard letters were delivered within one working day throughout the State in the quarter from April to June. This compares to a ComReg target of 94 per cent. ComReg said 78 per cent of standard letters were delivered within a day in the same quarter of last year.
The ComReg commissioner Mike Byrne said that after recent discussions, An Post was now reviewing its service and the regulator would be updated shortly.
He said the service in Dublin was a particular worry. "ComReg is anxious to understand the apparent decline in performance of mail originating in Dublin for delivery nationwide or indeed locally, and whether there any particular problems in Dublin that may be attributing to the poor performance of Dublin addressed mail," said a statement.
Mr Byrne said business and residential customers required a dependable postal service.
While the national figures were a concern, Dublin is suffering from worse service - with only 69 per cent of mail posted in Dublin delivered by the next day.
Some 97 per cent of mail was delivered within three working days. ComReg said this fell short of its 99.5 per cent target, but was the first suggestion of an improvement during the last 12 months.
The survey is carried out by TNS mrbi and is independently audited. An Post disagrees with the findings of ComReg's surveys, saying its own research throws up different figures.
Most of the postal system has been liberalised, with private companies able to compete for any letters or parcels with a weight above 50 grams. However, it is illegal for companies to offer to handle the post of standard letter items. In line with an EU schedule, full market opening is due to take place in January 2009.
An Post and ComReg have disagreed over recent years about the need to allow An Post to increase its prices. ComReg has said price increases have the potential to stop growth in the use of the service.
