LONGUEUIL, Que. -- Bloc Quebecois Leader Gilles Duceppe says he'd be in favour of invoking the constitutional notwithstanding clause to buttress legislation banning the wearing of niqabs at citizenship ceremonies.

"Basically, I'd be for introducing the clause if ever such a law was found to contravene the charter," he said Tuesday.

The constitutional measure was put in place for "precisely for this kind of situation," he added.

When the Conservatives tabled legislation last June to ban the wearing of niqabs at citizenship ceremonies, they said it respected the federal charter.

The federal government is currently seeking a stay of a court decision that overturned a ban on facial coverings at citizenship ceremonies.

Ottawa will appeal last week's Federal Court of Appeal ruling that would have allowed Zunera Ishaq to wear a niqab while swearing the oath of citizenship.

It said it would ask for the ruling to be deferred while the issue is before the Supreme Court.

Should that happen, it is unlikely Ishaq would become a citizen in time to vote in the Oct. 19 federal election.