Fuel laundering and smuggling by ex-IRA gangs and border criminals in the Republic has been almost totally defeated, the Irish taxman has said.
A Revenue official told the State's public spending watchdog a survey this year of filling stations provided "authoritative evidence" that the apparent multimillion-euro trade is close to being put out of business.
"The fuel laundering problem has been effectively eliminated," the accounting officer told the Comptroller and Auditor General (C&AG). The claim was made as part of the C&AG's audit of efforts by Customs to tackle fuel laundering.
The watchdog said a series of initiatives hit the underground business and that no evidence of laundered fuel was found in tests on 197 licensed traders this year.
It also pointed to the success of a joint exercise by Revenue and the UK's Revenue and Customs to introduce a new fuel marker on both sides of the border in April last year to make it harder to launder diesel.
Despite the Revenue claim, Public Accounts Committee chairman Sean Fleming said: "Shockingly, there is no revenue estimate of the loss to the Exchequer as a result of fuel laundering. There has to be a better way of dealing with this issue and we will consider all options in relation to these taxes."
The C&AG was told by Revenue that it does not estimate how much the black market operations were costing.
The Revenue claim came months after an independent report estimated the Irish Exchequer lost €239m (£207m) last year through illegal laundering.
The C&AG said new licensing of fuel traders and electronic reporting have made it more difficult for gangs and that reckless trading provisions introduced in 2013 are a further deterrent.
Revenue said a national sampling of fuel in September last year found just 2.9% of samples test positive for the new marker, and a random sampling exercise in January this year found no evidence of the new marker.
From 2011 to 2015 a total of 149 service stations were forced to close because they were unlicensed or breached their licences.
The report showed 47 commercial seizures of laundered fuel were made last year involving 215,132 litres.