The Prime Minister vowed to act on proposals submitted last month by the Advisory Group on Campaigning and the Voluntary Sector to allow non-charitable social advocacy groups to run ads.
A Green Paper, setting out the Government's constitutional reforms, said it would "explore the options for enabling charities to better campaign on issues that are likely to advance the cause of the purpose for which they have been established".
The paper also revealed that the membership of pressure groups had grown, while that of political parties had fallen, and that organisations such as Make Poverty History played "an ever more important role in driving social, economic and environmental change".
The 2003 Communications Act outlaws broadcast advertising by "political bodies" and ads that are"directed towards a political end". One option is for "political" ads by pressure groups to state that they include political content, represent the opinion of the advertiser and disclose the source of the ad's funding.
The timescale for change is unclear, but legislation could take up to two years. Charities also want Ofcom and the BACC to recognise they cannot have a political purpose.