Innocent until proven guilty -- that's why House Speaker Nancy Pelosi refuses to remove New York Rep. Charles Rangel from his powerful chairmanship of the House Ways and Means Committee.

As the House Ethics Committee investigates a string of allegations against Rangel, who represents New York's Harlem district, a spokesman for Pelosi said Friday that the "bipartisan process" should be allowed to finish before the congressman's fate is decided. 

The committee voted unanimously Thursday to expand its probe of Rangel, who faces numerous allegations spanning several years, including alleged failure to pay taxes and disclose as much as $1.3 million in income that he earned from multiple properties.

Pelosi thinks removing Rangel from the chairmanship of the powerful tax-writing committee before the ethics probe is completed would undermine the American principle of innocent until proven guilty, said Drew Hammill, the speaker's spokesman. He said Pelosi does not believe her decision weakens the public perception of congressional ethics. 

"We have a bipartisan process in place. It should be allowed to finish," Hammill told FOXNews.com. "We are confident the committee will conduct a thorough review and then report to the full House."

House Majority Leader Steny Hoyer echoed Pelosi's position, telling FOXNews.com that "yesterday's statement shows that the bipartisan ethics committee is doing its work."

A handful of House and Senate members have been the subjects of government ethics probes, and there appears to be no record of anyone ever being stripped from a committee role pending the outcome of an active investigation.

Sen. Robert Packwood, R-Ore., resigned from office in 1995, a day after the Senate Ethics Committee recommended he be expelled from office for abuse of power, including "repeatedly committing sexual misconduct" and "engaging in a deliberate... plan to enhance his personal financial position."

In 1982, Sen. Harrison Williams, D-N.J., resigned after an ethics committee found that his conduct in the Abscam scandal, a public corruption investigation, was "ethically repugnant." Williams -- along with five members of the House and one member of the New Jersey State Senate -- was convicted on numerous charges, including conspiracy, bribery, and conflict of interest.

The House Ethics Committee on Thursday said it had reviewed more than 12,000 pages in documents, conducted 34 interviews and held 30 hearings into allegations against Rangel.

The committee's decision to expand its probe came just a day after House Democrats shot down a Republican-backed resolution to remove Rangel from his chairmanship pending the outcome of the investigation.

The Congressional Black Caucus, of which Rangel was a founding member, sent a letter to Pelosi on Thursday blasting the vote as "partisan attempts to ignore the well-established, bipartisan congressional ethics process."

"Regrettably, the minority has repeatedly attempted to make an end-run around the bipartisan procedures for investigating possible ethics issues," the letter read. "These Republican attempts to presume guilt before an investigation has been completed violate the core American principle of the presumption of innocence."

Rangel's office condemned the measure as a "highly partisan effort."

"Let's look at this resolution for what it really is -- a highly partisan effort designed to undermine the important work in Congress on health care reform," a Rangel representative, who declined to be named, told FOX News.

But critics say Pelosi should strip Rangel of his chairmanship if the Ethics Committee found sufficient evidence to widen its investigation.

"Given the expanded investigation-- it is past time for Speaker Pelosi to insist that Chairman Rangel step aside until the Ethics Committee completes its work," House Minority Leader John Boehner said in a statement Thursday.

"The American people won't stand for having a chairman of the House's tax-writing committee who is under investigation for not paying his taxes. What more has to happen before Speaker Pelosi does the right thing?" he said.

Rangel, who has served in the House for nearly 40 years, reportedly failed to report as much as $1.3 million in income from 2002 to 2006. In 2008, the New York Post reported that he failed to disclose $75,000 in rental income.

In June 2009, the House Ethics Subcommittee opened a probe of Rangel's trips to conferences in the Caribbean, and in August Rangel disclosed more than $500,000 in previously unreported assets.

"These are glaring tax violations and he has paid no penalties or interest," said John Stone, a spokesman for Rep. John Carter, R-Texas, who is leading the effort to oust Rangel from his post.

"It's setting up a double standard," said Stone. "The average American gets slapped with fines and possible jail time, while the rich and powerful can get off 'scot-free.'

"He's chair of the very committee that oversees internal revenue of the tax code. He simply cannot serve with this massive question and these constantly expanding investigations," he said.