The Labour leader said he would legislate to ensure Which? and Citizens Advice would be given a say in setting the agenda of the Competition and Markets Authority.
He said Labour would be "the party of the consumer" and the plan for an annual competition audit of the economy would help ensure that areas where regulators were failing would be identified and tackled.
He said: "Unless you bring the consumer into the heart of these things, we are not going to get the change we need, we are not going to shine the light on these broken markets."
He added: "The Competition and Markets Authority scrutinises competition across the board.
"They will be working with Which?, the CAB and others to say 'where are the areas where competition isn't working, what are your members telling you about where we need to act?'"
Which? executive director Richard Lloyd said: "We would welcome a closer relationship to help set clear priorities for competition, consumer protection and market reform. We look forward to seeing more detail on how these proposals would work in practice."
But the chief policy director of the Confederation of British Industry, Katja Hall, warned: "The role of the Competition and Markets Authority is to act as an independent body.
"It should operate free from interference and not be told how do its job by other stakeholders."