OTTAWA — Conservative Sen. Mike Duffy submitted expense claims while Parliament was dissolved during the last federal election, reporting he was on Senate business on days he appeared to be campaigning for the party.

The full extent of Duffy’s Senate expenses during the writ period remains a mystery — the Conservative government is refusing to reveal the full breakdown of the senator’s claims and his repayment of $90,172.24.

But independent auditors at the firm Deloitte listed Duffy as being in Ottawa on Senate business and claiming a daily expense for seven days in April 2011, a month that was dominated by campaigning for the May 2 vote.

He was also listed as being on Senate business at an “other location� on another six days. Using cellphone records, Deloitte managed to catch one inappropriate “other location� claim from 2012 while Duffy was in Florida.

But the auditors said they remained in the dark about whether taxpayers paid his expenses on many other days, since Duffy failed to fully disclose his activities and records.

Social media and newspaper reports offer a glimpse of how Duffy’s busy campaign schedule overlapped with the Senate business he reported to auditors:

— On April 5, Duffy spoke to the Kootenay-Columbia Conservative association in British Columbia. His travel claims indicated he was on Senate business.

— On April 8, candidate Sandy Lee tweeted that she was meeting Duffy in Norman Wells, N.W.T. Lee’s campaign paid Duffy $209.01 in expenses. His travel claims indicated he was on Senate business.

— On April 21, Duffy was reportedly campaigning with candidate Scott Armstrong in Nova Scotia. Armstrong’s campaign paid Duffy $409.91 in expenses.

— On April 28, Duffy appeared to have a busy day in the Toronto area, campaigning with candidates Maureen Harquail, Wladyslaw Lizon and Gin Siow. Lizon’s campaign paid Duffy $169.45, as did Siow. His travel claims indicated he was on Senate business.

— On April 29, former cabinet minister Lawrence Cannon tweeted a picture of Duffy at an event outside of Ottawa that same day. The Deloitte audit listed Duffy as being in Ottawa on Senate business and claiming a per diem.

If Duffy collected daily Senate expenses while on the Conservative campaign trail, taxpayer may have paid twice: Conservative candidates who paid for Duffy’s hotel stays would have received federal rebate money for those expenses.

Duffy’s campaign events did not end there. On at least five other occasions documented in media reports, Duffy campaigned with Conservative candidates. He did not tell Deloitte about his campaign calendar, forcing Deloitte to list his activities as “undocumented.�

Meanwhile, the public Senate attendance register does not cover April or May 2011, the period that Parliament was dissolved.

“We are not on a leave of absence — Parliament was dissolved — we are still senators. However, all party work we are doing is paid for by the party,� Duffy told Postmedia News during the campaign.

“MPs continue to be paid. So do we.�

Duffy did not respond to a phone call or an email message requesting comment.