BT's offer to deliver universal high-speed broadband has been opposed by the Country Land and Business Association (CLA).
Ministers have already promised to implement a new broadband Universal Service Obligation (USO) that ensures everyone in Britain has a legal right to request minimum speeds of 10Mbps by 2020.
However, BT's offer means many premises would receive speeds substantially faster than 10Mbps. As a result, the proposal could render the planned USO unnecessary.
This has prompted concern from the CLA, which said the USO is necessary because it creates an "inalienable right that can be enforced by the premise owner".
Ross Murray, President of the body, said: "It cannot be replaced by a cosy deal with just one company allowing it to deliver connections how it sees fit."
Murray stated that accountability for delivering the rollout of broadband has been "a closed shop discussion between the industry and the regulator for too long".
This, he said, would end if the USO was implemented and make the consumer "the enforcer".
"It's no wonder BT Group doesn't want that," he remarked.
Murray said the CLA will therefore fight any attempt to "water down the hard won legal right to broadband for rural homes and businesses".
"For too long, rural areas have been at the back of the queue when it comes to investment in infrastructure and that is why this legal principle is not something to compromise on," he added.
Culture Secretary Karen Bradley has said the government will look at whether BT's plan or a regulatory approach would work better for homes and businesses.
However, she stressed that the "driving force" behind choosing between the USO and the BT proposal will be "making sure we get the best deal for consumers".