Sen. Russ Feingold confirmed Monday his opposition to the financial regulatory reform compromise hammered out last week by a House-Senate conference committee, saying it does not have the safeguards necessary to prevent another crisis.

The Wisconsin Democrat’s opposition to the measure could stymie his party’s efforts to deliver the package to President Barack Obama before Congress adjourns for the July Fourth recess at the end of this week. The majority is already down one of the votes that it needs to overcome an expected Republican filibuster because of the death of Sen. Robert Byrd (D-W.Va.).

Meanwhile, Sen. Scott Brown (R-Mass.), who voted for the Senate version of the bill — Feingold did not — has indicated he might withhold his support because of a $19 billion tax on banks and hedge funds added to the conference report.

In a statement released Monday afternoon, Feingold said the legislation has some merits but not enough to garner his vote. “As I have indicated for some time now, my test for the financial regulatory reform bill is whether it will prevent another crisis. The conference committee’s proposal fails that test and for that reason I will not vote to advance it,” he said. “During debate on the bill, I supported several efforts to break up ‘too big to fail’ Wall Street banks and restore the proven safeguards established after the Great Depression separating Main Street banks from big Wall Street firms, among other issues. Unfortunately, these crucial reforms were rejected.”

Feingold complained that “Wall Street lobbyists and their allies in Washington continue to wield significant influence on the process.”

Feingold, among the most liberal Members of the Senate, is in a competitive race for re-election this year.