CORRECTED-UPDATE 1-Canadian prime minister's top aide quits over expenses scandal
(Corrects 20th para to show Novak is principal secretary not deputy chief of staff)
* Expenses crisis threatens to undermine government
* Conservatives trailing in opinion polls
* Opposition demands probe into scandal
By David Ljunggren
OTTAWA, May 19 (Reuters) - The top aide to Canadian Prime Minister Stephen Harper abruptly resigned on Sunday over his role in an mounting expenses scandal which is threatening to undermine the Conservative government.
Nigel Wright, Harper's chief of staff, quit after secretly giving a C$90,000 ($87,000) check in February to Mike Duffy, a member of the upper Senate chamber, to help him cover living expenses he had improperly claimed. News of the gift leaked late on Tuesday.
Opposition legislators said the check broke ethics rules that forbid senators from taking presents and made a mockery of the government's repeated promises to increase accountability in Ottawa. Duffy, a former national television journalist, resigned from the Conservative caucus on Thursday.
Wright's departure reflects the pressure Harper is under. Officials told reporters on Friday that the chief of staff - who says he did not tell Harper about the check - would be staying. Continued...