Senate Majority Leader Harry Reid reiterated his unsubstantiated claim that Mitt Romney may not have paid taxes for a decade in remarks on the Senate floor this morning.

The Nevada Democrat upped the ante, calling on the presumptive GOP presidential nominee to disprove the allegation, which Reid has repeated in comments to several reporters this week. Reid’s contention has not been corroborated, and he has declined to name the Bain Capital source he said told him about Romney’s failure to pay taxes.

“So, the word’s out that he hasn’t paid any taxes for 10 years. Let him prove that he has paid taxes, because he hasn’t,” Reid said. “We already know from one partial tax return that he gave us, he has money hidden in Bermuda, the Cayman Islands and a Swiss banking account. Mitt Romney makes more money in a single day than the average middle-class family makes in two years or more.”

Reid’s comments came during another disagreement with Senate Minority Leader Mitch McConnell (R-Ky.) over process and after McConnell gave a speech highlighting the 65 times that Reid has used procedural maneuvers to prevent Senators from offering amendments on the floor.

The dispute arose as a pending cybersecurity bill stalled on the floor in another process dispute this morning.

“As of this morning, 29 Democrat Senators have filed 74 amendments, not counting the ones used to fill the tree. That’s a lot of amendments that won’t get votes,” McConnell said. “Instead of just being rubber stamps for the Majority Leader, I would encourage these Senators to stand up for themselves and their constituents and demand to be heard.”

Republican amendments filed included proposals to repeal the 2010 health care and financial regulation laws, as well as one to bar late-term abortions in the District of Columbia.

Reid says Republicans are trying to undermine progress, repeatedly using the Romney tax return disclosure issue as a foil for GOP arguments about priorities on job creation and the economic recovery.

“He refused to release his tax returns, as we know. If a person coming before this body wanted to be a cabinet officer, he couldn’t be if he did the same refusal Mitt Romney does about tax returns,” Reid said.