Investment managers have made little change to how they purchase research using dealing commission despite a Financial Conduct Authority crackdown earlier this year.
The regulator published a May policy statement confirming investment managers may only use client dealing commission to pay for "substantive" research, and not for corporate access.
More stringent EU-wide rules are set to be outlined later this year as part of MiFID II regulations.
But a survey by regulation consultants Cordium found 72% of investment firms had made little or no change to their processes. More than two-thirds of respondents described corporate access as a "free service".
Just a fifth said they have made "significant" changes.
Will Morrell previously led the FCA's thematic review of dealing commissions before joining Cordium this summer. He said: "The fact that so many still believe that corporate access is a free service is worrying.
"It is unlikely that the service is being provided for free and if corporates are not paying a retainer to the broker then the logical conclusion is that it is being cross-subsidised by other services.
"As a rough rule of thumb, it is safe to assume there is no such thing as a free lunch and firms should be able to evidence to the FCA that they are not inadvertently paying for corporate access.”
Roughly half of respondents said they would pay less for research if the cost came directly from the management company's profit and loss statement.
Under the existing FCA guidelines, investment managers are barred from using dealing commission to pay for access to senior corporate figures.
In July, Investment Week reported the regulator was in "active discussions" with one asset manager on client redress after finding too few firms correctly assessed the benefits, and cost of, such research.
The regulator said its review, which encompassed 17 investment managers and 13 brokers, found "only two investment managers operating at the level we expect".
