By David Ljunggren
OTTAWA, Oct 23 (Reuters) - Canada's main opposition leader accused Prime Minister Stephen Harper on Wednesday of creating a "culture of corruption" as Harper faced an expenses scandal that looked to be spiraling into the biggest crisis of his seven years in office.
Harper's Conservatives have been under pressure since May, when it emerged that his chief of staff had privately given a check for C$90,000 ($86,540) to help a senator repay expenses that the government said were improperly claimed.
Nigel Wright, the chief of staff, resigned a few days later. Harper, who came to power in February 2006 promising to boost accountability in government, says he knew nothing of the check that Wright gave to Senator Mike Duffy.
But Duffy told the Senate late on Tuesday that when Harper ordered him in late February to pay back the money, Wright had been in the room too, and he said that two lawyers from Harper's office had helped arrange the check.
"We know that Stephen Harper hasn't told the truth. He has to start telling the truth," said Thomas Mulcair, leader of the official opposition New Democratic Party. "This is a profound scandal that directly implicates Stephen Harper ... (he) has created a culture of corruption."
Harper's office - which called Mulcair's comments "incorrect" - said the prime minister told Duffy in February to repay the money and had never spoken to him again about the expenses.
"The prime minister never knew about, or discussed, the agreement between Wright and Duffy. He has been clear and consistent on this point," Harper's chief spokesman, Jason MacDonald, said in an email.
The next federal election is scheduled for October 2015. Polls show the Conservatives trailing the Liberals, who are led by Justin Trudeau, son of former Prime Minister Pierre Trudeau, with Mulcair's NDP in third place.
Duffy and two other Conservative senators - all appointed by Harper - have quit the party caucus amid questions over their expense claims.
Trudeau called for all those involved to testify under oath about what happened.
The Conservatives, who have a majority of seats in the Senate, the upper house of Parliament, pushed to suspend Duffy and the two other senators without pay. Duffy said this smacked of tactics used in Iran or Russia.
"I wish I had had the courage to say 'no' back in February when this monstrous political scheme was first ordered," he told the chamber on Tuesday. "Today you have an opportunity to stand strong and use your power to restrain the unaccountable power of the prime minister's office."
Patrick Brazeau, the second of the three senators the Conservatives are targeting, told the Senate on Tuesday that the party was engaging in political abuse of power.
"If this is the Harper government's way of believing in democracy and exercising democracy, I think we should all be very fearful. This is a complete joke, a complete farce and, Stephen Harper, you lost my vote," he said.
The third senator, Pamela Wallin, is due to address the Senate later on Wednesday.
($1=$1.04 Canadian) (Reporting by David Ljunggren; Editing by Peter Galloway)