Conservative senators have blocked a Liberal move to hear from a Deloitte executive about his possible interference in the audit of Senator Mike Duffy's expenses.

An RCMP affidavit released last week suggests that Michael Runia called a more junior Deloitte employee at the behest of Conservative Senator Irving Gerstein as the Prime Minister's Office and party leadership scrambled to rein in a scandal over Duffy's spending.

Runia is the Ontario managing partner for Deloitte's audit section and the auditor of record for the Conservative Fund of Canada, the Conservative Party's fundraising arm.

Gerstein runs the Conservative Fund.

Elections Canada records show Runia regularly donates the maximum allowable amount to the Conservative Party.

While the Senate's internal economy committee invited three Deloitte representatives to Thursday's meeting, Runia wasn't one of them.

Liberal Senator George Furey argued at the end of the meeting that the committee needs to hear from Runia, but outgoing committee chair Gerald Comeau overruled Furey's motion.

Comeau said it was up to the RCMP to investigate the call if they so chose.

"Consider this a challenge of your ruling, chair," Furey said.

Senators voted to sustain Comeau's ruling, meaning the committee won't call Runia to explain the call.

Liberal Senator Joan Fraser later served notice in the Senate she would move a motion next week to have the upper chamber direct the committee to call on Runia to testify.

'I wanted that call ... to end'

Gary Timm, who was in charge of Duffy's audit, told senators on the committee that Runia phoned him once.

"He wanted to know if Senator Duffy were to repay, how much would that be. I told him I can't divulge or disclose any confidential information. He understood my reply and I directed him to public information," listing senator entitlements, Timm said.

"It was a short call and it ended there."

Asked whether Timm tried to find out why and on whose behalf Runia was calling, Timm said no.

"I wanted to keep everything confidential and I wanted that call, like I said, to end shortly... He called me about that one question," Timm said.

Despite Timm's response to Runia, a March 21, 2013, email from then-PMO staffer Patrick Rogers suggested he had information about Deloitte's not-yet-drafted report. The email was contained in the 80-page RCMP affidavit. None of the allegations in the affidavit have been tested in court.

Rogers said in an email that Deloitte wouldn't make a finding on Duffy's residency, something borne out in the final report.

"That paragraph was troubling for us too," said Alan Stewart, a partner at Deloitte Forensic.

'Objectivity maintained' at all times

Timm went to Stewart and Peter Dent, also a partner at Deloitte Forensic, about the call. They decided not to tell the two Senate audit steering committees about the call since Timm had given Runia no information.

Stewart and Timm said they don't report to Runia because he's the senior partner for Ontario, while a separate partner manages the Toronto section in which Stewart works. There's a further separation, they said, because they work in the forensic section rather than the audit section in which Runia works. Stewart and Timm report to Dent.

"We can assure you that no confidential information was provided out of the investigative team to anyone other than the two Senate subcommittees that we were dealing with, and the Senate administrative people that we were dealing with, and our objectivity was maintained at all times," Stewart said.

"So [Runia] would have no influence on your audit whatsoever?" Liberal Senator Paul Massicotte asked.

All three Deloitte employees said he wouldn't.

"Hard to believe," Massicotte said.

Files kept in secure room

Senators tried to drill down into who could have provided information to Conservative officials, with a dozen people working on the audits of Duffy, Patrick Brazeau, Pamela Wallin and Mac Harb.

Stewart said some team members worked on only small aspects of the Senate audits. The files were kept in a secure room with padlocked filing cabinets and two laptops with digital files cut off from the internet. None of the team members were allowed to bring mobile devices into the room, he said.

Still, seven people had access to the full report, Conservative Senator Elizabeth Marshall pointed out.

"Are you confident that the confidentiality of the report was maintained?" she said.

"Yes," Timm and Stewart replied.

Stewart said none of the committee members phoned him or other members of the team for updates on the audit.