The consumer watchdog says it has received almost 200 complaints about fuel price gouging in the past two weeks.
The Competition and Consumer Protection Commission is appearing before an Oireachtas Committee later.
It will outline how some consumers alleged filling stations colluded to increase petrol and diesel prices despite a government reduction on excise duties.
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Chairperson of the Enterprise Committee, Sinn Fein's Maurice Quinlivan, says people are angry.