Five Fifa sponsors have written to world football's governing body to demand "cultural change" and "independent oversight" of reforms.
Adidas, McDonald's, Coca-Cola, Visa and Budweiser parent company Anheuser-Busch sent the letter to Fifa this week as it discusses reform proposals.
Following a string of corruption allegations levelled against the organisation which have culminated in American and Swiss investigations as well as the suspension of president Sepp Blatter, Fifa is under intense pressure to clean up its practices.
Following the indictment of nine Fifa officials and five corporate executives on charges of corruption from the US Department of Justice, Blatter launched the reform process while announcing his intention to resign.
Sponsors were initially promised a place on the Fifa reform committee to help guide the process, but have since only been offered places on an advisory board.
In the letter sent to Fifa, its major sponsors - with the exception of South Korean car manufacturer Hyundai and Russian state-backed gas company Gazprom - called on the organisation to allow external influence in its reform process.
The sponsors' letter reads: "We want to stress that we are calling on you to embrace change, implement reforms, endorse a long-term independent oversight approach and initiate the cultural change because we all want to see football thrive.
"We know that you, the Executive Committee members, will soon be considering a list of reforms aimed at strengthening Fifa's governance.
"Transparency, accountability, respect for human rights, integrity, leadership and gender equality are crucial to the future of Fifa. Reforms can set the proper framework for these characteristics, but a cultural change is also needed."
In response, a Fifa spokeswoman has insisted sponsors' views would not be sidelined. "We share their passion for the game and are committed to working with them to embrace positive changes so that we can fulfil our mission of promoting football around the world," she said.