A dozen senators who filed questionable expense claims have seen their amounts owing reduced by a special arbitrator.

Former Supreme Court justice Ian Binnie has ruled that most of the 14 senators did not overbill as much as originally thought.

In a report last year, the auditor general said the 14 owed taxpayers a total of $322,611 for disallowed expenses. After combing through all the senators' records, Binnie has upheld approximately 55 per cent of that total, saying the senators need to back $177,898 instead.

Binnie reduced the amounts that 12 of the 14 owe, but decided that Senators Lowell Murray and Dennis Patterson still needed to pay the full amounts flagged by the auditor general.

While some senators saw tens of thousands shaved off their amounts owing, one senator, Robert Peterson, saw his bill reduced by 39 cents, while Senator Terry Stratton now owes 30 cents less than he was first told.

The new amounts owed range from a low of $404.45 for Senator Donald Plett, to a high of $38,023.27 owed by Senator Sandra Lovelace Nicholas.

Binnie said, for the most part, the senators didn’t overbill out of malice, but out of a misunderstanding of the rules.

"I impute no bad motives to any of the senators," Binnie said in his report. “They acted in accordance with what they believed to be their entitlement. Our disagreement, where it exists, is as to the content of that entitlement.”

Binnie told reporters that many of the senators and their staff were confused about the rules.

"I found, for the most part, the attitude was, 'If we knew the rules, we would follow them,"' Binnie said. “In other words, I didn’t feel for the most part that they were ‘gaming’ the system.”

Auditor general Michael Ferguson noted the questionable expenses last year in a critical audit of Senate spending, finding nearly $1 million in problematic expense claims from 30 current and former senators.

Of those 30, 14 chose to go through an arbitration process led by Binnie. Another nine paid back the money, and seven opted out of arbitration.

The 14 senators who went through arbitration now have 30 days to reimburse the amounts owed. If they fail to repay, they could have their salaries garnished.

The RCMP began investigations into all 30 senators’ expenses, but last week, announced that they had dropped 24 of those investigations.

One of the senators the RCMP is still investigating is Colin Kenny, who took part in the special arbitration. Binnie ruled that Kenny still owed $27,458, down from the $31,628 the auditor general flagged.

Much of that total came from disallowed travel expenses. Binnie noted in his report that Kenny made several trips from Ottawa to Vancouver, Victoria, Edmonton and Toronto over two years for meetings with contacts and journalists.

Binnie called the frequency of these visits “totally out of proportion” to Kenny’s parliamentary functions, especially since Kenny was not on any Senate Committees or working groups at the time and was “essentially freelancing his own public policy agenda.”

Senator Jean-Guy Dagenais said he welcomed Binnie’s findings but said he would launch a formal complaint with the College of Chartered Professional Accountants of Ontario against Auditor General Ferguson, accusing him of negligence and breach of professional duty.

"He never checked the information we had provided him and he soiled my reputation by publicly doubting the existence of the parliamentary activities. He had a job to do and he did not, despite the $ 24 million that the check will cost Canadian taxpayers," Dagenais said in a statement.

Patrick Boyer, a former progressive Conservative MP and author of "Our Scandalous Senate," said in an appearance on CTV's Power Play Monday that Binnie's rulings haven't cleaned up the red chamber’s problems.

"In fact, any Canadian who's still feeling frustrated or outraged today has every justification for being that way," said Boyer.

"The Senate continues … to be a public institution run like a private club. The senators made all those rules about their expenditures –- by the way, a number of senators have managed quite handily to figure out what the rules are and have not run afoul of any problems –- so it seems that the rules aren’t such a problem as those who are interpreting it."

Boyer said that Sen. David Tkachuk, the former chair of the internal economy committee, made assurances several years ago that he had "two sets of eyes" in place to review every invoice submitted before any public money was spent.

"Well, if they did and all this money was spent, including that of which is the subject of three criminal trials -- Mike Duffy's concluded and two yet to come -- then clearly this is a problem that we have with an unaccountable Senate," said Boyer.

Boyer also disagreed with several senators who he said issued press releases on Monday, saying that Binnie's ruling had "vindicated" them.

Boyer also added that Binnie's ruling will allow senators to continue to do things they've done in the past, including "raising party funds on the public dime."

"This is where (senators) hope the traffic cop doesn't show up, because if there's a real adjudication of these issues there's still a lot that will damn and condemn the Senate," he said.