WASHINGTON (CNN) - The House Ethics Committee voted unanimously Thursday to expand its investigation of Rep. Charlie Rangel, one of the most powerful members of Congress.
The committee is now looking into Rangel's alleged failure to disclose hundreds of thousands of dollars worth of assets on mandatory congressional financial disclosure forms.
The prominent Democrat, whose district includes the Harlem neighborhood of New York City, has been under investigation for a year over several issues relating to financial impropriety. He has admitted to failing to pay taxes on $75,000 in income from a rental property he owns in the Dominican Republic.
Rangel heads the influential Ways and Means Committee - the lead body for writing tax law in the House of Representatives. He has said he is the victim of a smear campaign by some in the media.
"As a practical matter, today's announcement is nothing new," said a statement issued by Emile Milne, Rangel's personal spokesman. "Today's action by the committee is a technicality, as everything they referenced in today's announcement has already been subject to ongoing review by the ethics committee and its staff.
"It is clear that the committee is being very thorough and deliberative in their process, hence today's announcement."
On Wednesday, House Democrats defeated a resolution that would have forced Rangel to step down from his chairmanship for the duration of the investigation.
The resolution lost in a mostly party-line 246-153 vote.
House Minority Leader John Boehner issued a statement Thursday urging House Speaker Nancy Pelosi to force Rangel to step down.
"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?"
House Majority Leader Steny Hoyer refused to say if Rangel should step down. He told CNN the Ethics Committee needs time to do what "they ought to do. I don't think we ought to draw conclusions from that because they're doing an investigation."
–CNN's Brianna Keilar and Deirdre Walsh contributed to this report