Update: Gardaí have revealed details of their operation targeting non-nationals operating taxis using fake licences.

Up to 90 officers carried out 10 raids on houses in Lucan and north inner city Dublin at 8am today.

The Garda National Immigration Bureau operation uncovered 134 cases where the immigration status of people who applied for or held a Public Service Vehicles (PSV) licence holder or PSV applicant is of concern.

They have finalised 64 investigations which have been forwarded to the Irish Naturalisation and Immigration Service and this has resulted in the revocation of 55 immigration permissions.

Of those 55 cases, 25 people are subject to deportation proceedings to date. Four have been arrested on foot of deportation orders with two already removed from the country.

Gardaí said a further 15 people are being investigated for having marriages of convenience, another seven have been found to be present in the State without any immigration permission, and are now subject to immigration controls, with one arrested for immigration-related offences.

Earlier: Taxi scam involving 180 non-EU nationals uncovered in Dublin - reports

A Garda investigation has found that 180 non-EU nationals are operating taxis using fake licences.

According to the Irish Independent, the scam was uncovered after four drivers were found to be operating taxis through fraudulent SPSV licence applications.

Several searches were carried out at residential addresses in Dublin as part of Operation Vantage, a four-year investigation by the Garda National Immigration Bureau.

Addresses in the north inner-city, Lucan and Palmerstown were targetted due to suspicions that false documentation, including SPSV applications, were being produced.

In total, 180 individuals have so far been identified in the operation, which has included officials from the National Transport Authority and the Irish Naturalisation and Immigration Service.

Fianna Fáil's Transport Spokesperson Robert Troy says the scam exposes a severe weakness in the National Transport Authority's system for processing taxi licences.

“The majority of taxi drivers in Dublin and elsewhere around the country are operating fully in line with all law and regulation, and it’s important to point out that this discovery is not a reflection on their hard work," he said.

"Rather, it exposes a severe weakness in the National Transport Authority’s system for processing taxi licences.

“It’s only reasonable for there to be concerns now for the integrity of the system in place to process taxi licence applications.

That this level of manipulation could have occurred is not only worrying for the public as a whole but for all other taxi drivers that pay a huge amount of money for a legitimate licence.

He thinks Transport Minister Shane Ross has serious questions to answer:

“The Minister with responsibility for the NTA has an obligation to provide clear answers on how this has happened, what's more, how long this illegal practice has been going on and failed to be picked up," he said.

In a statement, the NTA said licensing of taxi drivers falls under the remit of An Garda Siochána.

It said the Gardai is the licensing authority for the issue and renewal of SPSV driver licences – the licence to drive a taxi.

"The NTA is assisting the Gardai and did provide information to them which triggered part of the current focus of activity. As the licensing authority for taxi drivers, the revocation or suspension of SPSV driver licences for individuals currently holding such licences will be a matter for the Gardai and will be dealt with by them."