OTTAWA -- The NDP is challenging Conservatives and Liberals to put an end to taxpayer-funded partisan work by senators.

New Democrat ethics critic Charlie Angus issued the challenge Tuesday, arguing that senators should not be allowed to participate in their parties' caucus meetings, to fundraise for them or help organize election campaigns from their perch in the upper house.

"There is no justification for unelected people to be using public money and Senate resources in their role as partisan organizers and fundraisers," Angus told a news conference Tuesday.

NDP democratic reform critic Craig Scott argued that limiting the blatantly partisan activities of senators would be a step toward returning the disgraced Senate to its intended role as a chamber of sober second thought.

There are no New Democrats in the Senate so it will be up to what the NDP dubs the "old-line parties" to rein in the partisan activity of their senators, some of whom have been mired in a series of expenses scandals for most of the past year.

Indeed, the NDP proposals were unveiled just hours before RCMP documents were filed in court, expanding the investigation into dubious spending and expense claims by Sen. Mike Duffy.

In the documents, lead investigator Corp. Greg Horton alleges that Duffy defrauded the Senate by paying almost $65,000 to a friend who provided "little or no value for service."

"We're asking the other parties: Do you take the issue of corruption and misuse of tax dollars in the Senate seriously, yes or no?" Angus said.

"They need to say that they take this seriously. Otherwise, they're shrugging it off and they're going to continue to allow the corruption to continue."

Neither the Liberals nor the Conservatives responded immediately to the NDP ultimatum.

The NDP is also calling for a prohibition on any Senate-funded travel that is not directly related to senators' legislative duties.

And it's calling for a single ethics commissioner and ethics code to oversee the conduct of members in both houses of Parliament, rather than continuing with separate ethics officers for the Senate and House of Commons. That would require legislative change.

For now, the NDP is waiting to see if the other parties agree to voluntarily limit senators' partisanship and travel. But Scott said the party is prepared to introduce bills or motions, if need be, to try to force the issue.

The latest Duffy revelations come on top of the RCMP's investigation into Duffy's allegedly fraudulent housing allowance claims and his acceptance of $90,000 from Nigel Wright, Prime Minister Stephen Harper's former chief of staff, to reimburse the Senate for those claims.

The documents also suggest the RCMP probe of Sen. Patrick Brazeau's housing claims has also expanded to include allegations that Brazeau used his former father-in-law's on-reserve address in order to fraudulently claim aboriginal income tax exemptions.

The NDP wants to abolish the Senate. But since that can't be done any time soon, Angus said the party is proposing "baby steps" to improve the scandal-plagued chamber.

"Until we can actually get rid of them, there needs to be some accountability measures in."