The National Republican Congressional Committee on Wednesday afternoon fired back at Rep. Alan Grayson (D-Fla.) immediately after he defended his controversial "die quickly" comment on the House floor.

"Alan Grayson not only refuses to apologize, he is doubling down on his despicable remarks and he is dragging his party with him," said NRCC Communications Director Ken Spain. "This is an individual who has established a pathological pattern of unstable behavior."

On Tuesday, the freshman Democrat said during a floor speech "the Republican healthcare plan is this: die quickly." He expressed defiance today in another floor speech.

"I apologize to the dead and their families that we haven't voted sooner to end this holocaust in America," Grayson said on the House floor.

Grayson is considered a vulnerable member of Congress facing an uphill re-election fight.

Spain also called for House Speaker Nancy Pelosi (D-Calif.) to demand an apology from the congressman.

"He is derailing the national debate on healthcare reform and embarrassing his constituents as a result. Now, more than ever, Speaker Pelosi should end her silence and demand an apology,"