The Advisory Group on Campaigning and the Voluntary Sector has claimed that the commission rule which states that charities can engage in political activities only if these remain "ancillary" and do not become the long-term dominant means of carrying out charitable purposes, unfairly hits smaller organisations the hardest.
But Ben Hughes, chief executive of Bassac, the national network of multi-purpose community-based organisations, said the scale of the problem had been exaggerated.
"The legislative and regulatory issue is a distraction; it's not a barrier for community groups, because they don't tend to embark on structured mainstream campaigning," he said. "The real issue is capacity. These groups often don't have the skills or the understanding of how to lobby and negotiate."
Hughes said the lack of available funding was also a major hindrance and argued that the Government's focus on service delivery had exacerbated the problem.
But Brian Lamb, director of campaigning at the RNID, and a member of the coalition, said: "Other research shows charities are confused about how to interpret the dominant-ancillary clause."
Bassac's research is based on responses from 120 organisations and in-depth research with 30. It is due to be published next year.