A Coventry-based motorcycle group fears the future of offroad motorsport could be under threat due to Government rules over the payment of agricultural subsidies.
The Motor Cycle Industry Association is backing legal action against the Department for Environment, Food and Rural Affairs to overturn its rules which will prevent farmers from claiming grants if they allow motorsport events on their land.
Defra has told farmers they will not qualify for the Single Payment Scheme if they allow agricultural land to be used for any form of motor sports.
Currently farmers are allowed to use their land for walking, bird spotting, clay pigeon shooting, horse shows and car boot sales, but not motor sports.
As a result, hundreds of events are being cancelled because farmers are withdrawing permission for their fields to be used.
Events affected include trials, grass track races, plus the majority of enduro events and motocross.
The MCIA, which has pledged £10,000 to the legal fund, said the events had become financially untenable and homeless because of the new SPS rules.
Other aspects of motorsport to be affected will include motorcycle practice tracks, quad bike tracks, off-road car events and motorised aspects of corporate entertainment.
It is believed that more than 40 per cent of car competitions could be at risk and an even bigger proportion of motorcycle events.
The MCIA said Defra was expected to argue it had not banned motorsport as events can continue as long as farmers do not claim a subsidy for the land used.
However, the income from motorsport is usually a fraction of that available from subsidies so the farmer has no choice but to cease allowing his land to be used, the organisation said.
Legal action has been initiated by the Land Access and Recreational Association and a fighting fund created to help pay the legal costs which may be incurred in defence of offroad motorsport.
Craig Carey-Clinch, of MCIA, said: "Defra has left the motorsport community with no choice but to initiate legal action, which is why MCIA has contributed £10,000 to the LARA Fighting Fund on behalf of the wholesale motorcycle trade. "