A Tesco supermarket employee is at the center of a legal dispute over lottery winnings, after she accidentally issued a ticket to a customer and then claimed it as her own.

Andrea O'Reilly from Navan in County Meath reportedly issued a customer with a €9 ticket; he later requested a less expensive ticket and was given a €4 one.

O’Reilly claims that she reissued the cheaper ticket to the customer before taping the €9 ticket to the side of her cash register. It later emerged that this ticket had a combination of winning numbers, making it worth €500,000 ($714,000).

The 26-year-old Tesco worker maintains that she had planned to pay for the ticket, but she was prevented by her employer. She now plans to sue her employer of six-and-a-half years.

In normal circumstances, a cashier can void the lottery ticket by scanning the bar code, however in Ireland the process is more complicated with lottery agents often having to call National Lottery Headquarters to fix mistakes.

Speaking through her solicitor Michael Shanley, O'Reilly said: "It's common practice that an employee has the option of purchasing a ticket that was issued to a customer."

"All I have to say at this stage is that I had the ticket and I now no longer have it," she told the Irish Independent.

A spokesman for Tesco confirmed the company have received legal notification from O’Reilly’s solicitor but wouldn’t comment further.