The federal Conservatives are moving to claw back benefits for a trio of senators appointed by Prime Minister Stephen Harper and later suspended amid the ongoing expenses scandal.

Tuesday's federal budget included a pledge to preserve the "integrity of parliamentary operations" by passing a law to ensure that suspended MPs and senators cannot, while suspended, accrue years of service that are ultimately used toward calculating the parliamentarian's pension.

The budget says only that the move will "prohibit Members of the Senate and the House of Commons from accruing pensionable service as a result of having been suspended from Parliament through a majority vote by their peers." Details of the bill, which has not yet been tabled, are unclear.

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"Canadians expect that all Parliamentarians will be held to the highest standards of accountability and that the integrity of our public office and institutions will be protected," the budget says.

Senators Patrick Brazeau, Mike Duffy and Pamela Wallin were all suspended in the fall amid ongoing reviews of their expense claims. Mr. Brazeau has since been charged with fraud and breach of trust following an RCMP investigation.

The trio were all appointed by Mr. Harper. While suspended, they don't collect a salary but still get some benefits and are able to accrue years of service. When that was revealed following the suspensions, the Harper government had objected to the interpretation of the rules – the budget signals they'll change the rules altogether.

RCMP continue to investigate the circumstances around expense claims by Ms. Wallin and Mr. Duffy, whose claims were repaid after he received a $90,000 cheque from Mr. Harper's then-chief-of-staff, Nigel Wright.

All three are eligible to return to the Senate after the next election, and resume collecting a paycheque, unless suspended again.

Ex-Liberal senator Mac Harb was also recently charged after an RCMP investigation, but retired in August and is no longer a senator.

The Senate scandal has dogged Mr. Harper since it erupted last spring. His party's poll numbers have sunk and many questions remain unanswered. Mr. Harper has said he did not know of the deal between Mr. Wright and Mr. Duffy, and RCMP found no evidence he did.

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Before the cheque from Mr. Wright to Mr. Duffy was revealed, the Conservatives asked the Supreme Court for a formal ruling on what powers the government has to reform the Senate, such as by introducing term limits or electing Senate nominees. The Court is still considering the case.

While pointing a finger at his ex-senator and ex-chief-of-staff, the Prime Minister has, however, continued to stick by some of those who RCMP say knew details of the repayment plans, including Senator Irving Gerstein, the Conservatives' chief fundraiser.

The NDP have called for abolition of the Senate, though the legal path to doing so is unclear and would almost certainly require reopening the constitution. Liberal leader Justin Trudeau sought to distance himself from the Senate by kicking out senators from his party's caucus – though he'd previously voted against a nearly identical NDP motion, and the exiled senators continue to call themselves Liberals.