Executors of the singer's estate claim money from a film deal and merchandising contracts has "flooded" into Michael's bank accounts since he died in June.

They predict the pop superstar will make another £60 million by the end of the year, and expect him to overtake Nirvana rocker Kurt Cobain and Elvis Presley – who have made £450 million and £362 million respectively from beyond the grave - as the highest-earning dead celebrity in the next 12 months.

Lawyer John Branca, who is co-executor of Michael's estate, said: 'Clearly this will be a new record for estates that likely will not be broken. Elvis' estate makes £33million a year. This will be a bigger estate.'

Branca and fellow co-executor, music executive John McClain, have put together a series of deals for commemorative coins, school supplies, a coffee-table book and a film.

They have also been retrieving funds held for Michael by anonymous creditors, thought to amount to "several million pounds", and tallying the value of the singer's property, memorabilia and art collections.

While Michael's earnings steadily increase, his older sister La Toya has spoken about her grief at her sibling's passing.

She said: "It's a very difficult moment for all of us. It's almost - you don't believe it - so you try to do the best you can by feeling his love, by helping and doing something he would want you to do."

Meanwhile, law enforcement sources claim Michael's doctor Conrad Murray had Propofol hidden in the singer's house.

Police officers found three large bottles and five smaller vials of the anaesthetic stashed in a closet in Murray's bedroom at the star's Los Angeles home.

They also believe Murray received regular shipments of the powerful drug – reportedly used to help Michael sleep, and believed to have played a part in his death – through courier service FedEx, which he then hid in other locations.

The search warrant used to raid the Las Vegas pharmacy frequented by Murray showed investigators were looking for FedEx records relating to "the purchase, transfer, receiving, ordering, delivery and storage of Propofol to Dr. Conrad Murray".

Police were also looking for credit card receipts relating to a purchase of Propofol the doctor made in May.