The gold medal is now set to be awarded to New Zealand's Valerie Adams, who had won the event in Beijing in 2008.

Ostapchuk, 31 (pictured top), tested positive for metenolone twice, once in an out-of-competition test on the eve of the shot final on August 5 and then again after she had won with a throw of 21.36 metres the following day.

Both her A and B samples have been tested and found to contain the prohibited substance.

Russia's Evgeniia Kolodko has been upgraded to the silver medal while China's Lijiao Gong is promoted to bronze.

The decision to strip Ostapchuk of the title was taken by an International Olympic Committee (IOC) discplinary panel headed by Germany's Thomas Bach and which also included Denis Oswald and Frankie Fredericks, both members of the ruling Executive Board.

Belarus' National Olympic Committee claimed that Ostapchuk had passed a pre-Olympic drugs at the end of July in Minsk.

"They had no explanation as to why such substance would have been found in the sample of the Athlete," said the IOC in a statement.

"Having seen the analytical reports of both the A and B analysis of both the First Sample and of the Second Sample, the Delegation did not doubt such substance was in the body of the Athlete."

They have now set up an enquiry to investigate the case.

Nadzeya Ostapchuk (centre) celebrates her London 2012 victory flanked by the silver and bronze medallists, New Zealand's Valerie Adams (left) and Russia's Evgeniia Kolodko

It takes to six the total of gold medals won by New Zealand during London 2012 and lifts them to 15th in the overall table.

Adams' defeat by Ostaphuck was the first time she had lost to the Belarusian for nearly two years.

Her rivals disqualification means that Adams becomes the first woman to retain the Olympic shot put title since the Soviet Union's Tamara Press, who won at Rome in 1960 and Tokyo 1964.

"I am speechless with this news," said Adams, who threw 20.70m at London 2012.

"It is taking me some time to take this in.

"It is huge and I am absolutely thrilled of course.

"It makes me extraordinarily proud as a New Zealander.

"It is also encouraging for those athletes, like myself who are proud to compete cleanly, that the system works and doping cheats are caught."

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