The lack of a unified regulatory system for China's fledgling carbon offset market has led to wild variations in prices in different regions, causing uncertainty among both buyers and project developers, traders said Tuesday.

China's national carbon offset registry was launched earlier last month, allowing offsets - known as Chinese Certified Emissions Reductions (CCERs) - to be transferred between buyers and sellers on the country's seven pilot emissions trading schemes.

The move was considered an important first step in China's plans to create a unified national carbon scheme from 2016, but price discrepancies between the pilot platforms could make it harder to harmonize the markets.

China aims to use carbon markets as a key tool to halt the growth of its emissions by the end of next decade.

CCERs are generated by low-carbon projects that have been approved by the National Development and Reform Commission. While they are cheaper than regular permits, they can only cover 5 to 10 percent of a firm's emissions. Regional carbon market regulators can also exclude any offset type they feel does not benefit their markets.

Beijing and Shanghai - the only markets to have finalized their rules on offsets - both banned the use of CCERs generated from emission cuts achieved before 2013, ruling out 99.5 percent of the 14 million CCERs issued so far.

As a result, prices have varied significantly. Spot deliveries offered to Beijing are priced at 25 to 30 yuan ($4.00 -$4.80), but the most accepted forward contracts stand within the range of 5 to 20 yuan, according to brokers.

Wang Kelei, China director of Greenstream, a Finnish carbon trader, said the uncertainties made it difficult for participants to plan their budgets. He said CCERs should be around one-third of the price of local permits.

The confusion could also cut profits from developers and deter investment.

"We have to look very carefully at the different eligibility restrictions in the various regions," said Susan Zhu, director at Shanghai Treasure Carbon, which recently co-launched a 200 million yuan carbon fund.

The ban on pre-2013 CCERs in Beijing and Shanghai could depress prices for offsets from older projects, and might cut compliance costs in those markets that choose to accept them.

That would add to an already significant cost differential in the pilot schemes. Beijing-based firms already pay around 53 yuan for each permit, compared to 20 yuan in South China's Guangdong Province.

"How the markets perform is largely determined by the strictness of local emission cap setting," said Kou Weiwei, director of Carbon Trading Capital, a UK firm developing projects in China.