One of the UK's biggest agricultural shows would lose more than £1 million if changes to school holidays are approved, its organisers have warned.
The Royal Welsh Show, which takes place during the first week of the school summer holidays, would face 'seriously financial harm' if the changes go ahead.
Last year, the Welsh government outlined proposals which would see the summer break shortened by one week.
The Royal Welsh Agricultural Society (RWAS), which runs the show, said it was 'strongly opposed' to the proposal.
Preliminary calculations show that the changes would lead to a loss of income in excess of £1 million, from reduced gate sales, membership, and camping revenue.
A spokesperson said: The summer break could be reduced by one week, meaning schools would be open during the Royal Welsh Show.
"As one of our major cultural festivals, the school holidays should embrace events such as this as they are vitally important for our culture and the Welsh language."
Almost a quarter of a million people visit the Royal Welsh Show annually and it is considered to be the largest agricultural show of its kind in Europe.
The society puts the economic impact of its event in excess of £40 million and there is approximately £10 million visitor spend during the event itself.
While RWAS said it was "not against the principle of modifying the school year", it urged the government to reconsider its current proposals.
The spokesperson added: "We are extremely concerned about the impact these changes will have, including taking away the ability for young people, families, teachers, and school staff to attend the show.
"In addition, thousands of children compete at the Royal Welsh Show each year, in both young farmer competitions and young handler and junior classes.
"This proposed change would remove the opportunity for young people to compete at the show, and to learn and showcase their skills."
The changes would also lead to reduced attendance, RWAS warned, affecting the trade for exhibitors and catering vendors.
Furthermore, the proposal would result in 'major practical implications', as the show hires over 50 school buses for the park and ride facility each year.
If schools remain open during the show week, these buses will not be available, the society said.
The spokesperson said: "Events such as the Royal Welsh Show are fundamentally important to promoting the industry and bridging the divide between urban and rural communities.
"As a charity, we are actively engaging more with the public, creating a better awareness of the importance and wider value of Welsh agriculture.
"We are extremely concerned that these changes could harm the future success of the show, thus having a major long-term impact on our culture and the prosperity of the language."
Over the coming weeks, the society said it would be collating evidence to support its objection to these proposals.
The Welsh government is currently seeking responses to the consultation on the reform of the school year, which closes on 12 February.
