The RSPCA has been advising horse owners of new legislation set up to deter fly-grazing.
The control of Horses Act came into effect in May with the intention of preventing, and helping to swiftly resolve, the practice of putting horses on private and public land without permission.
The law brought England in line with Wales, which introduced a similar law early last year. Charities estimate the number of horses fly-grazing to be more than 3,000.
It means owners who graze their animals on private land can have their horses seized by the landowner and wither sold or otherwise disposed of within four days.
The owners can be charged for any damage to the land, as well as for the care of the horses.
Its is hoped the new law should also put the onus back on owners to comply with other legislations, such as compulsory microchipping, as any horse found to be fly-grazing will only be returned if it has been microchipped.
RSPCA assistant director of public affairs David Bowles said: “This law will make a big difference to horse welfare, as landowners can be more quickly deal with fly-grazing animals, instead of leaving them on unsuitable land without grazing, shelter or additional food, which is all to often the case.
“It is now time for irresponsible owners to remove illegally grazed horses and to provide them with proper care. They should also be getting their horses microchipped. Otherwise, they could lose their animals completely if they persist in fly-grazing.”