A raft of prize money increases for the Victorian spring carnival have been announced along with significant bonuses attached to feature races.

Star filly Mystic Journey is the Cox Plate favourite and will be eligible for a $1 million bonus should she win the $5 million weight-for-age feature at The Valley in October, courtesy of her wins in the Australian Guineas and All-Star Mile during the autumn.

Those two races are among 13 feature Victorian races this year in which the winner of any of those is eligible for a $1 million bonus should they also win the Cox Plate.

The $13 million in increases announced on Thursday has come from contributions from Racing Victoria, the Victoria Racing Club and the Victorian government.

Along with the recently announced upgrade of the Melbourne Cup prize money to $8 million, a host of other feature races during this year's Melbourne Cup Carnival at Flemington have received significant increases.

They include the Group One VRC Sprint Classic (1200m) and Group One Cantala Stakes (1600m) both increasing from $1 million to $2 million, while the Group One Coolmore Stud Stakes for three-year-olds and Group One Empire Rose Stakes for fillies and mares have received $500,000 increases.

An additional $8 million is being invested across 63 Group and Listed races throughout the spring in Victoria.

During the Caulfield Cup carnival, prize money for the Group One Thousand Guineas has been doubled to $1 million while the Blue Sapphire Stakes has also been boosted from $350,000 to $500,000.

The Moir Stakes at The Valley has also received a boost and will now be one of two $1 million Group One sprints run under lights at the track during the spring.