Wallin told a Toronto radio station (NewsTalk 1010) Thursday that the payback created a perception she was guilty of fudging her expenses.
Wallin, who was co-hosting a three-hour talk show, said she paid back some $38,000 despite her belief that many of the travel expenses in question were legitimate.
The former Conservative said she paid the money to end the distraction created by the Senate scandal, despite receiving advice not to pay it back.
Since then, she says, the payback has been used against her.
Wallin acknowledged she made mistakes in filing some of the expenses, but maintains that most of the claims she submitted were approved under Senate guidelines that she calls vague.
"I regret doing it," said Wallin. "I would pay back what I think I owed, but not the large sum of the charges that were rung up because of retroactively imposed new rules.
"I just think it's given some people an excuse to say 'oh, well, you must be guilty because you paid it back'."
Wallin, along with fellow former Tories Patrick Brazeau and Mike Duffy, was suspended from the Senate in early November over the expense claims.
Liberal Mac Harb resigned from the Senate in August after paying back $231,000 for ineligible housing and travel expenses.
Harb and Brazeau were charged by the RCMP in February with fraud and breach of trust.
Duffy and Wallin have so far not faced any charges.
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