Duguid announced the staffer resigned after a report by CTV London that some of the minister's Christmas cards were sent out using a "franking" sticker usually available only to federal members of Parliament and senators.
Members of provincial parliament must use postage stamps on their Christmas cards, and the cost can be covered by their office budgets.
Duguid says the individual responsible for the mailings initially indicated that the postage had been paid and that he had followed the appropriate rules.
However, Duguid says late Wednesday, after more questions were raised, "it became evident this was not the case," so he accepted the staffer's offer to resign.
The minister says he will pay for any postage costs for the cards that did not have stamps, and will co-operate with any request for further information from Canada Post or the federal government.
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