Hundreds of self-funded retirees have shared concerns about what the proposed changes might mean for their incomes.
Labor's Matt Thistlethwaite came out swinging against the inquiry during a hearing in southern NSW on Monday.
He was furious a website about the committee inquiry, set up by chairman and Liberal MP Tim Wilson, had included a request for people to sign a Liberal Party petition against Labor's plan.
"That is unethical, that is improper use of parliamentary resources," Mr Thistlethwaite said.
The website uses the Australian coat of arms and says is it authorised by Mr Wilson in his capacity as committee chairman.
Mr Thistlethwaite also savaged Liberal MP Andrew Wallace for handing out party membership application forms during a hearing on the Sunshine Coast.
"That is an abuse of the parliamentary process," he said.
"We should rightfully be using these inquiries to inquire into government policy and proposals. But they should not be used as an opportunity for the Liberal Party to recruit and to sign petitions."
Mr Wilson accused the opposition of attacking the inquiry and trying to shut it down.
He claimed including the Liberal Party petition as a "required field" on the committee's website was an administrative error.
"There was a tick box somebody coded in which put the wrong requirement - that has been removed," he said.
"But the key point is that we're providing people with an opportunity to be able to provide their views and issues on this particular policy, because people have a right to be able to do so."
Labor's financial services spokeswoman Clare O'Neil accused the Liberals of shamelessly politicising the process.
"I am disgusted with the way the Liberals are abusing parliamentary process in order to essentially corral support for a policy that they don't particularly like," she told reporters in Canberra.
