Two horses, both six-year-olds, died during the meeting at Plumpton Racecourse on Sunday.
In the first race of the day, Head Rush was pulled up injured, halfway through the two-mile hurdle race in which he was competing.
Then, in the final event of the day, a National Hunt flat race, grey gelding Eastbury fell to the ground injured and was seen struggling to get up. Both horses were destroyed.
The charity Animal Aid says urgent action is required by both the racecourse and the British Horseracing Authority to prevent further horse deaths. They are not rare at Plumpton, the charity said – a total of 29 horses have perished at the East Sussex course since March 2007.
Michael Moloney, Chief Executive at Plumpton Racecourse, said: “We are very sad to have lost, Head Rush and Eastbury during racing at Plumpton on Sunday and our sympathies are with the connections of both horses.
“Horseracing is a sport that is very carefully regulated and monitored by the British Horseracing Authority, high standards of horse welfare are demanded, and none of our 16 fixtures held annually can take place unless key BHA welfare criteria has been satisfied.
“Despite the best efforts of all involved, as with participation in any sport involving speed and athleticism, the risk of injury can never be completely removed.
“In line with the national average over the past 10 years, the number of fatalities compared to runners at Plumpton has decreased, and we will examine closely the circumstances which led to both incidents.”