Senator Pamela Wallin has broken her silence over the Senate expense claims scandal, saying in an exclusive interview Thursday with CBC's Peter Mansbridge that she is sorry and that she takes responsibility for mistakes she made.

"I'm very sorry obviously that I've caused all of this grief for family and my friends and for my fellow parliamentarians, and I think taxpayers have a right to know," she told Mansbridge.

Auditors are currently going over Wallin's travel expense claims going back to January 2009, when she was first appointed to the Senate. It has been reported that Wallin has claimed about $350,000 in travel expenses since September 2010.

Wallin said she made mistakes on her claims for flights.

"I sign the documents, so I take responsibility," the former journalist and diplomat said. "I take full responsibility for this. I should have gone over it with a fine-tooth comb as anybody should and make sure, but I just didn't."

"I was doing what I thought my job was — to not sit in Ottawa in an office, not sit in the Senate chamber always, but to be out there," she said .

Wallin said that she has already paid back about $38,000. "There may be more. I don't know."

Asked why she hasn't resigned from Senate, Wallin said: "Because I want to see these issues dealt with. I am doing my level best to sort out my particular case and make sure that there are no more issues and no more concerns."

Wallin left the Conservative caucus in May and is currently sitting as an Independent until the audit into her expense claims is completed.

"It was clear to me that they wanted me out [of the caucus]," she said. "A phone call comes and you're given an hour to resign or you'll be fired… for lack of a better word."

Asked if her relationship with the Conservatives is over, Wallin said that is for others to decide.

Prime Minister Stephen Harper defended Wallin on the expense claims issue in the House of Commons back in February, but she said she has never talked with him on the issue.

While Nigel Wright, the former chief of staff to the prime minister, wrote a cheque to cover Senator Mike Duffy's expense claims, Wallin said Wright never offered to cover her expenses.

"These are my mistakes, and I will pay my bills," she said.

"He did not offer, I did not ask."

Wallin said she has also stepped down from some boards she sat on, "because I was becoming a distraction."

No report until end of July

Earlier Thursday, auditors with the firm hired to look into the housing and travel claims of four senators, including Wallin, told the Senate's internal economy committee that they expect their audit of her claims will be ready by the end of July, after the chamber breaks for the summer.

The audit of Wallin's expenses was originally expected to be completed before the Senate's recess starts at the end of June.

However, the auditors with Deloitte said they've been asked to look at claims going back to when Wallin was first appointed as a senator for Saskatchewan in January 2009. That represents a period three months longer than they were originally asked to examine.

Gary Timm of Deloitte also said auditors are waiting for information from a third party.

"Nobody more than me wants that report as soon as we possibly can," Wallin told Mansbridge.