The increasing number of international visitors to the spring carnival has forced Racing Victoria to implement new quarantine rules to prioritise space for the highest rated horses.

With just 24 positions available at the Werribee International Horse Centre and the strong possibility that demand may exceed space, the new rule will ensure horses highest in the order of entry for the Melbourne and Caulfield Cups receive preference.

Government regulations stipulate horses must spend two weeks in quarantine upon arrival in Australia. Last year 22 horses were quarantined at Werribee, an increase from 20 in 2011.

Racing Victoria Executive General Manager Greg Carpenter said the rule was made with the goal of ensuring the best possible runners make their way into the fields for the spring’s biggest races.

“Our overriding principle in determining which horses will be afforded priority access to the Werribee International Horse Centre will be to deliver the best quality fields for our internationally recognised Group 1 features,” Carpenter said.

“All of the Carnival’s major races have early nomination dates and thus we will rely upon the order of entry for these races to determine access to the facility, with preference given to horses highest up the respective orders.

“We felt it important to provide clarity around what horses would be excluded in the event demand did exceed its capacity.”

The spring carnival riches have become more popular with overseas horses in recent times and raiders have won two of the last five Melbourne Cups.