The advertising watchdog is to undertake a major review of the term 'unlimited' in mobile data plans.

Customers are often hit with extra charges after going over data limits.

The Advertising Standards Authority of Ireland (ASAI) says it has received dozens of complaints over the term.

The ASAI is currently finalising a guidance note for companies when advertising mobile and broadband services.

In relation to the word 'unlimited', the ASAI says it has identified this term as one to be "reconsidered".

It adds that a "comprehensive review" will include a consultation process with relevant stakeholders.

The review has not formally begun as the ASAI has been prioritising efforts on finalising the guidance note - it is not known when this will be finished.

A man texting on a mobile phone

But it says it will be looking at the conditions in which the term can continue to be used by advertisers.

In a statement, the authority explains: "The current situation is that the term 'unlimited' can be used when a plan has a fair use policy (FUP) when no more than 1% of existing customers on the unlimited plan are affected by the FUP threshold and when customers are advised that they are approaching the threshold.

"When we receive complaints in this area, we ask advertisers to provide us with data that shows on a month to month basis over the previous six-month period the number of customers affected.

"Our expectation is that providers continually monitor the number of users that have been affected and if the percentage who breach the FUP threshold rises to more than 1% of customers on the plan, that the thresholds be adjusted."