China on Thursday denied accusations it is blocking an agreement on corporate transparency at the upcoming G20 summit in Brisbane, which President Xi Jinping will attend.

Beijing has been waging a high-profile anti-graft drive and secured broad support for an international anti-corruption declaration at the Asia-Pacific Economic Cooperation (APEC) meeting it hosted this week.

But Berlin-based group Transparency International said China has rejected principles on beneficial ownership that would make it easier to establish who runs a company which Australia had hoped to unveil at this weekend's summit.

Anti-graft advocates have repeatedly called for tougher corporate disclosure requirements, arguing that such measures would help prevent the use of shell companies for illegal purposes.

China's ruling Communist Party is wary of disclosure requirements that might reveal the hidden wealth of the country's political elite, a topic considered off-limits by party leaders.

Transparency International senior programme coordinator Maggie Murphy said the advocacy group believes Beijing is blocking adoption of the principles.

"China has a lot to gain by adopting these G20 Beneficial Ownership Principles," Murphy told AFP. "They would help contribute to their strong anti-corruption crackdown and help track down the people syphoning funds out of the country.

"We hope that China has had the opportunity in the last few days to discuss any remaining reservations with Australia and other leaders and is willing to fully support them," she added.

A Chinese official denied that Beijing has sought to impede the talks -- and maintained that China did not have the power to do so even if it wanted to.

"China is not obstructing relevant discussions," said Zhang Jun, director general of the Chinese Foreign Ministry's Department of International Economic Affairs.

"G20 is G20," he said. "G20 is not the (United Nations) Security Council. China does not have veto power. No countries have any veto power and all discussions are based on consensus."

While China supports cooperation on the issue of beneficial ownership "on the whole", Zhang said, "in terms of company registration, different countries have different legal procedures and practices".

"We must accommodate the actual national conditions of each country in order to take consistent steps," he added.

- Extradition treaty -

Foreign news outlets that have released reports on the wealth of Chinese leaders' families have felt the consequences.

Bloomberg and The New York Times have had their websites blocked in China since they published investigations into the family fortunes of Xi and former premier Wen Jiabao in 2012, and Beijing has not granted visas for their new journalists.

Leaders at the APEC summit in Beijing said they backed the APEC Network of Anti-Corruption Authorities and Law Enforcement Agencies (ACT-NET), which will seek cooperation on tracking cases across borders.

They also agreed to step up nascent anti-corruption efforts with a regional commitment to "deny safe haven to those engaged in corruption, including through extradition".

Rights campaigners say Chinese courts are controlled by the government and do not provide fair trials, but Australia is still considering a separate extradition treaty to help Beijing track down corrupt officials.

China's in July launched its so-called "Fox Hunt" -- a campaign to repatriate officials or their family members accused of corruption -- but critics say the Communist Party has not introduced reforms to prevent graft, such as public disclosure of assets.