Rep. Peter DeFazio (D-Ore.), dressed as Sherlock Holmes, looks at Roxy the "TPP Tracker" bloodhound outside the Capitol on Oct. 29, 2015. Many House Democrats and advocacy groups have deemed the Trans-Pacific Partnership deal unfair to workers. (David Nakamura/The Washington Post)

A coalition of more than 1,500 interest groups is sending a letter to Congress on Thursday demanding that lawmakers block the Trans-Pacific Partnership (TPP), the 12-nation Pacific Rim trade pact championed by the Obama administration.

"The questions policymakers should be asking about these rules is whether, on the whole, they would create American jobs, raise our wages, enhance environmental sustainability, improve public health and advance human rights and democracy," the coalition writes in the four-page letter. "After careful consideration, we believe you will agree, the answer to these questions is no."

Labor unions, environmental groups, consumer advocates and faith groups are among the 1,525 organizations that signed onto the document, which was organized by the Citizens Trade Campaign. Hundreds of local labor union affiliates have signed on.

The effort comes in the same week that several big business organizations, including the U.S. Chamber of Commerce, formally endorsed the trade deal, which is among President Obama's top economic agenda items in the final year of his presidency.

Obama has said that the trade accord, which includes Japan, Mexico, Canada and Australia, will boost U.S. competitiveness in the Asia-Pacific region in the face of China's growing clout. Opponents of the TPP have said that the deal will lead to a loss of manufacturing jobs to Asian nations, harm the environment and increase the cost of some new-generation medicines in poorer countries.

"The TPP elevates investor rights over human rights and democracy," the letter states. The AFL-CIO, the American Federation of Teachers, Greenpeace and the Sierra Club are among the signatories.

Administration officials disputed the characterizations.

“TPP will not only provide a much needed boost to Made-in-America exports and the jobs they support, it will also help level the playing field for American workers and businesses through the toughest labor, environment and innovation protections of any trade agreement in history," said Matthew McAlvanah, a spokesman for the U.S. Trade Representative's office. "At a time when our competitors are actively working to write the rules of the road in the Asia-Pacific through agreements that would put our workers and businesses at a disadvantage, we can’t afford to sit on the sidelines.”

Obama bucked the majority of Democrats in pursuit of the deal, teaming with Republicans to pass legislation granting him "fast-track" trade powers in June, and negotiators for the 12 nations inked the final deal in October. The administration hopes that Congress will vote on the pact by this summer, but some GOP leaders have cited concerns with provisions related to the tobacco and pharmaceutical companies. Senate Majority Leader Mitch McConnell (R-Ky.) has suggested that the vote could be delayed until after the November presidential election or until a new president takes office next January.

The letter from opponents could have the most sway with the small coalition of 28 House Democrats who voted in favor of the fast-track bill. Under the terms of that legislation, Congress cannot amend the trade accord before holding a vote.

"The TPP does not deserve your support," the group writes. "Had Fast Track not become law, Congress could work to remove the misguided and detrimental provisions of the TPP, strengthen weak ones and add new provisions designed to ensure that our most vulnerable families and communities do not bear the brunt of the TPP’s many risks. Now that Fast Track authority is in place for it, Congress is left with no means of adequately amending the agreement without rejecting it entirely. We respectfully ask that you do just that."