The Office of the Scottish Charity Regulator should consider publishing charities' administration costs on its register, according to a report for the regulator.
The independent report, by market research company Scotinform, was based on two surveys that asked charity trustees and the public about their views on charity regulation.
It found that for Scottish people the area of most concern was administration costs for charities. They were also concerned about whether charities were properly regulated to ensure they were working for the public benefit.
"The OSCR could increase trust and confidence in charities by focusing on making the public aware of how it addresses these concerns," the report says. "One way of doing this would be to show the proportion of income spent on administration on the register."
But the SCVO, the umbrella body for Scottish charities, said the proposal could create confusion rather than clarity.
"Because administration costs are not recorded uniformly in charity accounts and the context for each charity is different, it would only be in detailed explanatory notes that the true position would become clear," an SCVO spokesman said.
He said the growing concern over public benefit highlighted in the report was the most pressing issue for the regulator to address.
The report examined surveys of 386 charity trustees and 1,006 members of the public to find out their awareness of the regulator, their views on its effectiveness and the areas of charity regulation it most needed to address.
Jane Ryder, chief executive of the OSCR, said: "Trustees generally have a positive view of the OSCR and the need for regulation, but there are areas we should examine, such as our reporting requirements.
"This is already being considered for the coming year."