Campaigners claim Prince Charles could "destroy" a quiet countryside village by providing land for a huge cattle market on their doorstep.
The Prince of Wales angered residents in Stretton Sugwas in Hereford by allowing his Duchy of Cornwall office to support the 25-acre plan.
They say the plot, opposite a primary school, will disrupt village life and cause noise and pollution. Proposers Hereford Council say the city centre cattle market is now inappropriate. There has been a city cattle market since the mid-19th Century.
The land is part of Prince Charles' 54,000-hectare Duchy estate and a Buckingham Palace spokeswoman said the Duchy supported the idea and was assisting through public consultation.
Solicitor Colin Gordon, leading the Save Stretton Sugwas campaign, said: "Stretton Sugwas is a small hamlet of 40 houses, a primary school and pub.
"Prince Charles visited the site and would have seen the project will devastate the village and adjacent school.
"The education and wellbeing of 100 primary school children will be impaired.
"The prince has been saying everyone should slow down and meditate but is promoting a development which will destroy a village. Stretton Sugwas will be overwhelmed."
Chairman of governors at Stretton Sugwas CoE Primary School, Shirley Williams, said:
"The governors are not happy - there will be increased air, noise and road pollution and increased traffic. We could lose students."
A Herefordshire Council spokeswoman said failure to relocate would prevent regeneration of the city and affect Hereford as a sub-regional centre. A spokesman for the Duchy of Cornwall said it supported regenerating the rural economy but the choice of site was the council's.