The International Equestrian Federation (FEI) has launched an investigation into allegations that Dutch eventer Madeleine Brugman used spiked boots in the warm-up to the show jumping phase at Barroca d’Alva last week.

FEI spokesman Malina Gueorguiev said: “Stewards and riders have said that the horse she [Ms Brugman] rode wore spiked boots.

“All the evidence that could be collected was collected, but the ground jury [at Barroca] could not make a decision and all the evidence has been forwarded to the FEI.

“We shall review the evidence and if necessary forward it to the [FEI] tribunal.”

Ms Brugman is trained by Australian rider Andrew Hoy, who was also riding at Barroca.

Spiked boots have sharp objects on the inside and are used to encourage the horse to pick its legs up over fences. If the horse hits the fence they cause it pain.

They are banned under FEI rules.