Washington (CNN) - Moments after narrowly losing a key vote on the hotly contested Wall Street reform bill Wednesday, Senate Majority Leader Harry Reid told a news conference that another senator "broke his word with me."
It was a rare public rebuke of a fellow senator, and while Reid, D-Nevada, and his aides refused to identify the individual or provide specifics about the charge, other Senate aides from both parties said Reid was referring to Scott Brown, the new Republican senator from Massachusetts.
An aide to Brown confirmed that the senator had signaled to Reid he would vote for the motion to end debate on the financial regulations bill, but said it was conditioned on changes that had not been made by the time of the Wednesday's procedural vote.
"Harry Reid does not speak for Scott Brown. Scott Brown speaks for Scott Brown," Brown spokeswomen Gail Gitcho said in response to Reid's accusation."Bipartisanship is a two-way street."
Gitcho said Brown didn't vote to end the debate "because the way this bill is currently constructed it would cost jobs in Massachusetts and does not include the fixes he understood were in the bill."
Brown later also confirmed the switch, saying that he told Reid on Tuesday he would support the motion to end debate on the financial regulations reform bill.
"Based on everything that's been happening, as you all have seen, it's been a bipartisan process, a lot of good debate. No BS," Brown told reporters in explaining why he initially supported Reid's motion. "But then we were kind of caught off guard with the fact that that we weren't getting the information from the leadership that we wanted. We made phone calls, we didn't get the proper response."
A spokesman for Reid, Jim Manley, refused to comment when asked if Brown told Reid his support was conditional on changes to the bill.
Brown and Reid were seen on the Republican side of the Senate floor having an intense discussion for several minutes after Brown cast his vote. The discussion ended with Brown disappearing into the Republican cloakroom.
The public dispute between Reid and Brown is unusual because Brown is a moderate Republican who already has crossed party lines on several occasions to give important wins to Democrats, and could do so again in the future.
One GOP source, who asked not to be identified, warned that Reid "can't haul off and call the one Republican you can rely on a liar."
Brown seemed unfazed by Reid's accusation.
"I never take any of this personally," Brown said. "I know that he's under a lot of pressure."
The motion to end debate needed 60 votes to pass, and it failed by a count of 57-42. Reid's Democratic caucus has 59 seats, meaning it needed one Republican vote to move forward on the bill.
However, it was unclear if the motion would have passed even with Brown's support. The final tally included a 'no' vote by Reid that he cast to ensure he could propose the motion again, as well as "no" votes by two other Democrats, while two Republicans voted "yes." One Democratic senator missed the vote.
The two Democrats who opposed ending debate, Sen. Maria Cantwell of Washington and Sen. Russ Feingold of Wisconsin, both said they wanted the bill's regulation of financial markets and trading to be strengthened.
Updated: 11:27 p.m.