The Data Protection Commissioner is set to prosecute companies who are continuing to bombard consumers with unwanted sales calls.
Around 120,000 people have signed up to a national database to avoid 'cold calling' but some companies have continued to illegally dial up their numbers.
The Data Protection Commissioner Billy Hawkes is now considering prosecutions against three separate companies.
"We have a number of people under investigation where there seems to be a case to answer. One of them is certainly well down the route towards prosecution and in the other two, the investigations aren't far enough advanced to decide that yet," said a spokesman.
The National Directory Database was launched last year to allow people to register their preference for avoiding cold calls. Companies who ignore this face fines of up to €3,000 for every call they make.
The Data Protection Commissioner is hoping that prosecutions will force the rogue companies to change their approach.
The number of complaints about unsolicited text messages, known as mobile spamming, dropped dramatically since the company, 4's A Fortune, was fined €1,500 for the offence at the Dublin District Court last year.
"The Commissioner's primary focus is on ensuing compliance. Hopefully it'll have an effect and we'll see a dramatic reduction this year in the amount of complaints we're receiving about cold calling.
"That isn't the case at present, because we're getting more complaints this year," said the spokesman.
The number of people signing up to the database, which is free of charge, is expected to increase gradually as consumers tire of sales calls for insurance, phone rental and other products.
Eircom and the other major telecommunications companies have sent out leaflets about the database in their phone bills in the last two months.
PA