Liberal MPs in Nova Scotia are reacting to news that Conservative Senator Mike Duffy was submitting Senate expense claims on days he was also campaigning for the party during the last federal election.

During the election in 2011, Duffy campaigned for candidates such as David Morse, Gerald Keddy, Greg Kerr and Scott Armstrong, billing them up to $409 dollars each for his expenses.

'Only an investigation, a full investigation, will determine whether Senator Duffy was in fact double dipping and charging the taxpayer at the same time.' —N.S. Liberal MP Scott Brison 

One incident in question includes a day when Duffy was campaigning in Nova Scotia with Conservative MP Scott Armstrong in the Cumberland-Colchester-Musquodoboit riding. Armstrong’s campaign paid Duffy $409.91 for his support.

Under federal election law, candidates get a 60 per cent taxpayer-funded rebate for expenses like Duffy’s.

The question is whether Duffy also claimed expenses from the Canadian Senate while on his three-day campaign swing through Nova Scotia in April 2011.

A Deloitte audit shows that Duffy claimed to be on Senate business in Ottawa while campaigning with Armstrong in Truro and Amherst on April 21.

During the previous two days in the province, it’s not clear whether claims were being made. Independent auditors at the firm Deloitte said Duffy has not fully disclosed his records, so they cannot confirm whether taxpayers paid the senator’s expenses on other days.

"There’s a lot of questions this raises and I think, really, it’s incumbent upon him if he wants to stay in the Senate, to start cooperating, to give full information to disclose what’s going on here," said N.S. Liberal MP Geoff Regan.

The prime minister's office said Thursday the Conservative Party is reviewing Duffy's expense claims from the 2011 campaign.

Duffy has been, at times, reluctant to explain his expenses. He stopped cooperating with Senate auditors when Prime Minister Stephen Harper’s chief of staff, Nigel Wright, wrote a cheque to Duffy for $90,172.24.

Liberal MP Geoff Regan said he’s calling on Duffy to fully disclose his records.

"Only an investigation, a full investigation, will determine whether Senator Duffy was in fact double dipping and charging the taxpayer at the same time " said N.S. Liberal MP Scott Brison.

Neither Duffy, nor representatives from the Senate returned calls from CBC News to explain what expenses Harper’s chief of staff was covering when he wrote a $90,000 cheque to the senator.