A group of campaigners led by comedian Mark Thomas is planning a demonstration outside Parliament to highlight the "absurdity" of the Serious Organised Crime and Police Act. The Act states that protesters must apply for a licence six days before demonstrating within a half-mile exclusion zone around Westminster.
The demonstration, which takes place on 22 September, follows another organised by Thomas last month.
Chris Stalker, head of NCVO's Campaigning Effectiveness Programme, which is part of a sector coalition lobbying for greater clarification of the Act, said: "We want the Government to issue guidelines to ensure the terms of the Act are applied reasonably."
The Campaigning Effectiveness Programme is also conducting an online survey of charities to find out their views on campaigning.