OTTAWA -- A spokesman for the prime minister says his office is working with the ethics commissioner's investigation into a $90,000 cheque cut by Stephen Harper's chief of staff to help a Tory senator.

But Andrew MacDougall says Harper still has full confidence in Nigel Wright, although Sen. Mike Duffy still has questions to answer.

Duffy has resigned from the Conservative caucus to sit as an independent amid a controversy over his housing expense claims.

He paid back some $90,000 in expenses after Wright gave him the money.

That cheque would appear to violate ethics rules that prohibit senators from accepting gifts.

MacDougall says Wright will remain in his job.