Hundreds of people seeking to change their mobile phone operator are facing lengthy delays because of a technical hitch with the industry's €30 million mobile number portability system.

The new state-of-the-art computer systems that enable mobile users to switch operators while keeping their entire mobile number, including prefix, stopped working on a number of occasions this week. This has created a huge backlog of customers who want to switch operators.

One irate customer who telephoned The Irish Times yesterday said she had been waiting for more than three days to change from O2 to Vodafone this week. Both operators had blamed the problem on each other's portability systems, said the user.

An O2 spokeswoman admitted there had been some small technical issues with the new porting system this week, which had affected about 50 of its users.

"It is a complicated process," said the O2 spokeswoman. "But we are quite pleased with the porting project since July 25th."

Vodafone said there had been problems at the early stage of this week but these had now been resolved and the backlog of requests had been cleared.

Industry sources said last night about 5,000 mobile customers had used the system and kept their numbers since it began operating late last month.

The computer systems, built at a cost of €30 million by the three mobile operators, are meant to be able to change a user's operator within two hours. But a series of technical hitches with the new system are causing delays.

Meteor said yesterday it had not experienced any problems with its own systems. But a spokesman for the company said it was suffering because of Vodafone's ongoing technical hitches.

"Vodafone's customer care is telling users who want to change to Meteor that the delay is our fault... Misinformation like this is to be deplored," said a Meteor spokesman yesterday.

Similar problems were experienced by users in Australia when it introduced a similar mobile number portability system in 2001. But the Irish industry believed these hitches should have been avoided in the Republic, where companies have been working on the plan for two years.

The Commission for Communications Regulation said yesterday it acknowledged that there had been delays and it was monitoring the situation.