(Alex Wong/Getty Images)

The House Budget Committee's top democrat picked a political fight with Sen. Minority Leader Mitch McConnell over campaign finance reforms during a speech Monday.

Rep. Chris Van Hollen, D-Md., challenged McConnell to be more specific in his critique of the DISCLOSE Act, Van Hollen's campaign finance reform bill that would require independent political groups that purchase ads designed to elect or defeat specific candidates to disclose the names of their top contributors.

"I have here in my hand a copy of the Disclose Act," he said, holding up a dog-eared copy of the bill during remarks at the conservative American Enterprise Institute in Washington. "I challenge Sen. McConnell - or anybody else - to show me where it selectively targets conservative groups."

McConnell previously blasted the Act as a "a backdoor effort to discourage those who disagree with the Obama administration from participating in the political process." The powerful Kentucky Republican also led the charge to block a previous version of the law in 2012, warning that the legislation, would subject members of conservative advocacy groups to "public intimidation and harassment" and allowed for the "creation of a modern day Nixon enemies list."

But on Monday Van Hollen dismissed McConnell's claim as "a bunch of nonsense."

"Their claim of selectivity is a red herring," he said. "You can't avoid disclosure because you might get your feelings hurt or face public backlash. That's part of the rough and tumble of a vibrant democracy and a spirited debate."

He called McConnell's support for other types of disclosures "a total double standard."

"Why is it in the public interest to require disclosure of a $200 contribution to a candidates' political campaign and not in the public interest to disclose a $200 million expenditure to elect or defeat that candidate?" he asked. "It's time for Sen. McConnell to stop saying the DISCLOSE Act is some kind of leftie conspiracy."

Van Hollen said donor transparency gives the public more information about who is trying to influence elected officials and aids in the enforcement of other campaign finance laws, like the prohibition against foreign donors.

In his address, Van Hollen also criticized 501(c)(4)s, which have funneled millions of dollars of "undisclosed money" into campaigns since the controversial Citizens United case in 2010.

The Maryland Democrat noted a "glaring discrepancy" between the statutory definition of a 501(c)4 - an organization "operated exclusively for the promotion of social welfare" - and the IRS's regulatory definition, which claims that "an organization is operate exclusively for the promotion of social welfare if it is primarily engaged in promotion in some way the common good."