Sen. Elizabeth Warren Monday issued a report slamming U.S. trade deals, citing "decades of broken promises," about enforcing fair labor standards.

Warren, D-Mass., has been one of the more outspoken Democratic critics of international trade deals and the report comes as the Senate prepares to vote on a bill that would give President Obama "fast track" authority to sign off on new trade deals.

The 15-page report, which includes three pages of citations, takes apart claims and promises by the Obama administration and proponents of trade deals that the agreements bring about increased enforcement of labor standards.

"This analysis reveals that the rhetoric has not matched the reality," the report concludes. "There have been widespread enforcement problems and flaws that prevent enforcement of the labor provisions of these free trade agreements."

Warren cites a report by the Government Accountability Office that found neither the office of the United States Trade Representative nor the Department of Labor monitors or enforces compliance with trade pact labor agreements.

The report points to "horrific labor abuses," in some countries, including Colombia, where 105 union activists have been killed since a trade deal with the United States was signed in 2006.

Warren is hardly the only Democrat opposing the Senate bill granting more authority to sign trade deals. Most Democrats oppose it, including Minority Leader Harry Reid, D-Nev.

Republicans are mostly in favor of the bill, but some want to amend it to curb currency manipulation, including former U.S. Trade Representative and now Sen. Rob Portman, of Ohio, who is up for re-election in 2016.