Experts say it is too fragile to make the journey Down Under.

The urn was to have been displayed in Melbourne and Sydney during the current Ashes series.

The decision followed six months of talks between the MCC and the Australian Cricket Board (ACB) to allow its temporary removal from the Lord's museum.

But scientists concluded there would be a real risk of breakage if the urn was subject to unnecessary movement or changes in humidity and pressure.

"At the final hurdle the MCC have advised us that it won't be possible," confirmed James Sutherland, the ACB's chief executive.

"We wanted it to come out so it could at least be shown in the capital cities of Australia so that as many Australian cricket fans as possible could get to see it at first hand.

MCC secretary Roger Knight explained: "We simply couldn't ignore the emphatic and authoritative advice that we received.

"Our absolute priority is to ensure that the urn receives expert attention from leading conservation specialists as a matter of urgency."

Australian captain Steve Waugh and leading bowler Glenn McGrath both advocate the idea of moving the Ashes to Australia.

And even Nasser Hussain conceded after his England team were beaten in 2001 that Australia should be allowed to take the Ashes home.