Washington(CNN) A member of the Federal Election Commission was defiant Tuesday after a nonprofit group said her request that President Donald Trump provide proof of voter fraud merited an investigation into whether her comments were inappropriate.

Ellen Weintraub's remarks were in response to a letter sent from the Cause of Action Institute to Lynne A. McFarland, the FEC inspector general, about a statement Weintraub made earlier in February. Weintraub called on the President to substantiate his claim of massive voter fraud in New Hampshire, a call she repeated in her statement Tuesday.

Cause of Action's letter said Weintraub, a Democratic member of the six-member commission, may be in violation of government ethics rules for making the statement as an FEC official and called on the agency's watchdog to look into the matter. The FEC is tasked with regulating campaign finance, and Cause of Action's letter said Weintraub could have stepped outside of her authority by commenting about voter fraud.

In a statement defending her authority to comment on the matter, Weintraub replied, "I will not be silenced."

Asked about the commissioner's response, Cause of Action acting President John Vecchione said, "We certainly aren't going to put our oar in on that. She's free to say whatever she likes. No one is silencing anyone."

Weintraub told CNN she saw it much differently, calling it "absurd" to parse the comments of an FEC commissioner speaking about a matter concerning federal elections.

"Honestly, I think this is an attempt to muzzle me," Weintraub said of the letter.

FEC commissioner asks Trump for voter fraud evidence

Additionally, Weintraub said it was within her purview to comment on the Trump administration's claim that illegal voters were bused into New Hampshire, because spending money to do so would likely constitute a campaign finance violation.

"I don't know how buses materialize without somebody spending money," Weintraub said.

The Cause of Action Institute is an independent group classified as a 501 (c) (3), meaning its work cannot be expressly political, and the group's website says its goal is to ensure "the federal regulatory process is open, honest and fair."

But a 2015 report from the Los Angeles Times connected the group with conservative megadonors Charles and David Koch, and tax records show the Franklin Center for Government and Public Integrity as well as Donors Trust are among its donors. Tax records also show contributions to the Franklin Center from Donors Trust, a Koch-affiliated group, and the Charles Koch Foundation.

Since winning the election, Trump has repeatedly alleged -- without offering evidence -- widespread voter fraud in the election. He has said in public and behind closed doors that "millions" of votes were cast illegally and were responsible for him not winning the popular vote.

There is no evidence of voter fraud anywhere near the scale Trump has alleged.

Trump said he would organize a formal investigation and bring evidence to the public, but has yet to sign an executive order establishing such a probe.