Four in five Britons now believe that many companies pretend to be ethical just to sell more products, a survey by Ipsos MORI for SEE Potential revealed.
As many as 80% of the consumers who took part in the survey said they would like to see more evidence to back up ethical claims.
The research has been published to coincide with the launch of SEE Companies, an accreditation scheme which hopes to give credibility to companies' green claims.
Companies that meet the scheme's standards will be able to display the SEE Companies logo on packaging and marketing materials.
Michael Solomon, founder and managing director of SEE Potential, said: "In the past two years, concern over issues like global poverty, working conditions in the developing world, species extinction and climate change has become more widespread. Business has reacted with claims of increasing responsibility.
"In some cases these claims have been based on solid SEE policies and practices but in others they have not. Until now it has been incredibly difficult to identify genuine SEE business."
SEE is a for-profit business that promotes socially-driven social, environmental and ethical business.