The British Horse Society is urging riders to lobby MPs as part of its campaign to improve equestrian access to forests.
The society said its recent postcard campaign made the Forestry Commission aware of riders' views on forestry access in England.
The Forestry Commission England's public forest estate extends to about 258,000 hectares.
This could provide miles of safe off-road riding which is badly needed for all sections of the equestrian community, the society said.
"While many forests in England allow equestrians free informal access, an increasing number discriminate against equestrians, requiring them to purchase a permit, whilst walkers and cyclists are allowed free access."
Many equestrians cannot afford to pay a permit fee, as 25 percent of horse owners earn less than £10,000 a year.
"Paying for access particularly discriminates against lower socio-economic groups," it said. "This discrimination is increasingly pushing riders into riding on the roads, which is inherently less safe, and less enjoyable, than off-road riding."
In England, horse riders currently have access to only 22 per cent of the public rights-of-way network, whilst carriage drivers have access to only five per cent.
The British Horse Society wants the Forestry Commission to sit up and listen and to treat equestrians the same as it does walkers and cyclists.
The society's director of access, safety and welfare, Mark Weston, said of the campaign: "We now need MPs to require the Forestry Commission to end their unfair discrimination against equestrians."