It has emerged that there have been no prosecutions so far relating to the petrol stretching racket which hit the county last year.
While one file has been prepared by local gardaí for the DPP, Dáil deputy Michelle Mulherin said this week that, for the most part, the racketeers behind the scam look almost certain to get away with their criminal activity.
Deputy Mulherin blamed the system, not the gardaí, for the situation.
Gardaí have so far investigated 150 complaints of petrol stretching and Revenue has investigated 44.
Petrol stretching refers to the practice of illegally adding stretching agents to fuel to boost profits. Motorists across Mayo who unwittingly filled up with the fuel have had their engines destroyed.
According to Deputy Mulherin the only way to stamp out the problem is to introduce widespread testing, including setting-up mobile laboratories, to identify bad fuel before it gets into people's engines, by which time it is too late to find the source.
"The system we have to counteract petrol stretching is reactive, not proactive, and is ultimately not delivering for the car owners who fall victim to petrol stretching," said Deputy Mulherin.
"Problems are only investigated after damage has been done to people’s cars. At that stage the contaminated petrol has gone through the engine and there is no fuel left to test."
Deputy Mulherin said the authorities took only 24 samples during checks on fuel delivery tankers across Ireland for the whole of 2014, making it relatively easy for criminals to get their contaminated fuel to the petrol pumps unchallenged.
"Contaminated petrol can easily be dumped in this jurisdiction from the North or UK," she pointed out. "There is a big gap between the problem occurring and the cars breaking down. But by the time this has happened the problem has moved on and can’t be detected."
Deputy Mulherin says a widespread petrol stretching problem has to be prevented from recurring in Mayo.