A decision to introduce a levy on horse manure has angered business leaders.
From July, the Government will charge equestrian businesses up to £500 to store muck as part of new legislation on industrial waste.
The Forum for Private Business has attacked the plans which will affect livery yards and riding schools.
Private horse owners will be exempt from the tax as any waste they produce will be classed as domestic, rather than industrial, waste.
Andrew Mowlah, of the FPB, said the legislation would hit smaller businesses hardest.
He said: "Yet again it appears the Government has failed to conduct a proper regulatory impact assessment and therefore small firms are going to be clobbered by this legislation. For small yards composting is a viable and much-used alternative. Our members are telling us that this new tax is absurd and has come completely out of the blue.
"Manure has been spread for as long as land has been farmed, it is ludicrous now to suddenly slap a stealth tax on the industry."
A muck heap of less than five tonnes will not incur a charge, but one of between five and 50 tonnes will cost £252 for the first year and £ 174 thereafter.
Fifty to 400 tonnes will cost £482 for the first year and £402 each year after that.
The average horse produces nine tonnes of manure every year.