The Country Land and Business Association – whose members provide 40% of all private rented rural housing – says proposals could have a negative impact on landlords and tenants.
It says the government is running out of time to make crucial amendments to minimum energy efficiency standards (MEES) set to come into force in the private rented sector.
New standards are due to come into force from 1 April 2018.
From that date it will be illegal for a private landlord to let a property with an energy performance certificate (EPC) rating lower than E to a new tenant.
The same rules will affect existing tenants from April 2020.
But the MEES regulations are still drafted as if supported by the Green Deal – despite it being scrapped in 2015.
CLA deputy president Tim Breitmeyer said clarity was needed as to whether those who own listed buildings or properties in conservation areas must comply.
Resolving the situation should be a priority for the government, said Mr Breitmeyer.
"Its failure to make any progress in two years since the Green Deal was scrapped is not good enough.
"With less than a year to go and the further delay of the general election, time looks to be running out."
The CLA claims that around one third of the homes set to be affected by MEES have been given lower EPC ratings than they deserve.
It says this is due to mistakes in the way the government assesses the energy efficiency of traditional solid wall buildings.
Although the government recently consulted on fixing these mistakes, it says there have since been no assurances these will be rectified before the April 2018 deadline.
Mr Breitmeyer said: "This has a negative impact on landlords, tenants and the government's own policy objectives."
The CLA supports the principles behind the MEES regulations.
But Mr Breitmeyer said there were so many errors, delays and uncertainties that it was almost impossible to advise anyone on how to be proactive and ensure compliance.
"Without the framework in place it is unjustifiable to ask landlords to act on the regulations when so much remains unclear," he added.
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