While European banks trumpet their accomplishments in terms of green finance a lack of transparency makes it impossible to verify their progress and leaves them open to accusations of greenwashing, an activist group said Wednesday.

ShareAction looked at the green finance commitments and activities of Europe's top 20 banks.

"Banks widely promote their green credentials to their customers and shareholders," said Xavier Lerin, senior research manager at ShareAction.

"However, there is a structural lack of transparency on what their green finance activities achieve," he added.

Banks are widely criticized for slow progress on the transition to net zero in their own operations as well as their lending activities.

The study found that all 20 have set green finance targets but only four — Barclays, BNP Paribas, ING, and Intesa Sanpaolo –- have published partial information on how they have calculated some of their green finance targets.

It also called into question some of the decisions on what was being counted towards meeting green finance targets, such as Spanish bank BBVA using deposits and Standard Chartered consulting activities. 

BBVA told AFP that the deposits supported loans backing sustainable projects while Standard Chartered declined to comment.

The study also criticized other practices like counting natural gas as a green investment, or different weighting given to projects in the accounting.

The study found that only 35 percent of the banks measure the real impact of their financing activities and even fewer specify whether the measurement is for new financing or includes existing projects.