Demand for carbon offsets - credits for emissions-reducing activity that can be generated through projects such as tree planting - is expected to increase as companies with net-zero goals buy them to cancel out emissions elsewhere.

But the market is unregulated, with many different standards and approaches making it difficult for companies to assess which credits they should use.

Critics of the market cite concerns including a lack of transparency and question the environmental quality of projects.

The Integrity Council for the Voluntary Carbon Market (ICVCM), an independent governance body, has published its criteria for projects to achieve its new Core Carbon Principle (CCP) standards.

The criteria "set a global threshold for quality which aims to unlock finance at speed and scale for projects to reduce and remove billions of tonnes of emissions that would not otherwise be viable," Integrity Council Chair Annette Nazareth said in a statement.

Until now, the most widely traded offsets abide by criteria established under the CORSIA scheme for the global airline industry.

CCP approval will require many of the same features as CORSIA, such as a project having quantified monitoring, reporting and verification standards, or being unable to go ahead without the revenue from the sale of carbon credits.

However, CCP credits will require additional measures, such as further governance checks. That could mean not all CORSIA credits will gain CCP status.

"We do expect this will have a significant impact on the market, but we can't prejudge the pre-designed assessment process we are about to start," ICVCM COO William McDonnell said in an interview.

Technology to capture and store carbon emissions at projects that also involve oil recovery will be excluded from the CCPs, as will any projects involving coal-fired power generation.

There could be instances where projects developing new gas plants could generate credits if they are for a major renewables installation and a back-up gas plant is included as part of the scheme.

The project would need to meet other requirements and result in clear emission reductions, ICVCM said.

It is not yet mandatory for a company retiring a carbon credit to disclose their name, but new standards would require their registration.

Once a credit has been retired it cannot be traded or used to meet climate targets by another company.

Industry groups welcomed the launch of the CCPs but said more needed to be done to build trust.

"The CCPs alone are not a silver bullet that can solve the challenge of carbon credit quality," Sebastien Cross, co-founder of carbon ratings company BeZero Carbon, said.

"Ultimately some projects will still be more effective than others - a spectrum of quality will always exist," he said.