A promotion for the world's best-selling beer encroaches on the protected breeding ground of the Tibetan antelope, according to Chinese conservationists who are campaigning against the commercial exploitation of one of the planet's most unique nature reserves.

Snow Beer – which is partly owned by the London-based SABMiller brewery company – is offering its customers an expedition to Kekexili, a remote region high on the Tibetan Plateau that is supposed to be off-limits to everyone except scientists with permission from the national government.

Marketing officials have said the tour – part of the company's annual "Challenging the World" promotion – will lift the veil on the "No Human zone" in Kekexili and promote environmental awareness. Participants are now being selected for a scheduled trip in October, but conservation groups are opposed on the grounds that it could encourage other companies and tour groups to enter a region that is famed for a dramatic conservation success story.

Kekexili – also known as Hoh Xil – is one of the least populated areas on earth. It has been a national reserve since 1995, but for many years after it was the site of a murderous conflict between poachers and the Wild Yak Brigade, a patrol of vigilantes committed to protecting endangered species.

Chief among them was the chiru, or Tibetan antelope, which was almost hunted to extinction due to the demand of wealthy foreign consumers for its fine shahtoosh wool. A gritty 2004 film about their plight and the killing of the brigade's leader prompted the government to strengthen protection. Chiru numbers have since started to recover and the animal was made a mascot for the Beijing Olympics.

Conservationists say the brewery's proposed tour would be a setback.

"This is China's most precious nature reserve. There are explicit prohibitions against crossings," said Wu Zhu, the conservationist heading the campaign against the promotion tour. "It has a 'No Human Zone', which as the name implies, is not supposed to be visited by anyone, yet Snow have gone ahead with their promotion even before they have permission."

The managers of Kekexili Natural Reserve said Snow Beer has requested permission to enter the region, but no approval has been granted. "We haven't decided whether to allow them to cross the outer band of the reserve, but they will definitely not be permitted to enter the core or buffer areas," said the director of the administration bureau, who gave only his surname, Wang.

There have been previous transgressions. The Chinese Academy of Sciences has reportedly brought businessmen to the area in the name of research, Ericcson is said to have taken in high-end clients and the Comfort Travel Agency in Shandong has offered trips for photographers.

"We have not paid enough attention in the past, but this time we will closely follow Snow," said Zhu.

The brewery is easier to target as it has strong brand and controls a fifth of the Chinese market. Thanks to the surging Chinese economy, Snow overtook Budweiser in 2008 as the world's most popular beer and now sells over 16bn pints a year. Other conservationists said there was a problem of social injustice if wealthy companies and individuals were allowed to buy their way into protected areas, though they did not rule out all human activity in the region.

"We have to consider whether visits are useful for overall conservation. In this case, Snow are only engaged in public relations. This is motivated purely by commercial interests," said Feng Yongfeng, of the Green Beagle NGO.

Snow Beer did not respond to the Guardian's questions. The company was quoted as telling the Global Times that its aim was to raise public awareness about Kekexili, "remove the mysterious mask of the uninhabited area" and "advocate the pioneer spirit of our brand".

• Additional reporting by Han Cheng