More than 100,000 euro was refunded to people in Ireland who contacted European consumer chiefs last year.
She revealed 60% of inquiries were successfully resolved with 112,058.69 euro refunded to the complainants, who included a woman whose teenage daughter was refused boarding on a flight in Spain as it was over-booked.
"More and more people are buying online and more and more people are buying cross-border," said Ms Harkin.
"While there are laws in place to help protect consumer rights, it can often be difficult to vindicate those rights because of language problems, different legal systems and attempted fraudulent trading."
Claims successfully resolved included an Irish person who found that goods bought from a UK trader were not as described in the purchase order and a Swedish consumer who ordered goods from an Irish trader that were not delivered and who had not received a refund.
Elsewhere a customer whose order was cancelled by a UK web trade without a refund was assisted, along with a holidaymaker who was billed and charged for "special cleaning" of a rental car from a French company. That claim was resolved following the intervention of the French European Consumer Centre and a full refund was made.
Ms Harkin said the data shows not only is there legislation in place that can protect the rights of people buying across EU borders, but that the centre will assist them in vindicating those rights.
"The European Consumer Centre in Ireland will investigate the case and contact the Consumer Centre in the country involved, as well as the company or trader concerned," she said at the launch of the report in Sligo.
"They will also provide information and advice where needed.
"This is a really good service and should help consumers navigate the sometimes tricky area of cross-border business."