New Zealand's Valerie Adams has been awarded the gold medal for the women's shot put at the London Olympics after the woman who beat her twice tested positive for a banned steroid.

Nadzeya Ostapchuk of Belarus beat Adams on the park with a best throw in excess of 21.35m, more than half a metre above Adams' best on the night.

But the International Olympic Committee said on Monday that Ostapchuk had been stripped of her title.

"The athlete was first requested to provide a urine sample for a doping control on 5 August. She competed the next day in the women's shot put event, where she placed first, and was asked to provide a sample straight after her competition," the IOC said.

"Both samples indicated the presence of metenolone, which is classified as anabolic agent under the 2012 Prohibited List."

Adams was overcome with emotion after being told she had retained her told.

"I am speechless with this news. It is taking me some time to take this in," she said from her base in Switzerland.

"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."

Ostapchuk was the 12th athlete at the Olympics to be excluded following doping tests, but the first to lose a medal.

The decision means New Zealand moves up to 15th on the Olympic medal table with a total of six golds, two silvers and five bronzes.

The Belarussian, the 2005 world champion, finished fourth at the Athens Olympics in 2004 and took bronze in Beijing four years ago.

NZ Newswire