A government official wrongly denied an immigrant his Canadian citizenship because he wrongly believed the man was mouthing the oath of citizenship rather than repeating it out loud, Citizenship and Immigration Canada says.

The mix-up took place at a March 29 ceremony, CIC said in a letter to the CBC's Evan Dyer.

"A citizenship officer at the ceremony determined that the candidate was not articulating the words of the Oath of Citizenship," said CIC spokeswoman Mary Jago.

"Subsequently, it was found that the officer made a mistake in the determination that the oath was not taken. The office has been attempting to contact the candidate to rectify the situation."

The man, whom CBC has not identified, was pulled out of line in front of his family while awaiting his citizenship certificate and was told he would not receive it.

Strict supervision of oath

CIC said the officer made a mistake and the man was not trying to avoid or alter the oath. They are looking for the man but have yet to find him.

The mistake comes after stricter supervision began around swearing loyalty to Queen Elizabeth, her heirs and successors.

Since December 2011, CIC has been watching to make sure all new Canadians recite the oath verbatim, which includes asking women to remove their veils.

Polls show a majority of Canadians would like to see the oath changed so new Canadians swear loyalty to Canada rather than Queen Elizabeth. Statistics show only five per cent want the oath to remain the same.