Ministers have shelved their previous plan to bring in legislation to change the 2003 Communications Act, which bans broadcast advertising by "political bodies" and ads "directed towards a political end".
Although no legislation on advertising was mentioned in Tuesday's Queen's Speech, government sources said it intended to give charities freedom to run political as well as fundraising campaigns.
"We will get there by another route," one said. "We now think the best way will be to change the rules governing charities."
It is unclear whether pressure groups that are not charities would benefit. Some have been denied charitable status in the past because their goals are deemed "political", but one option would be for this rule to be relaxed. Gordon Brown said: "It is important that charities are guaranteed the independence and the right to have their voice heard and to campaign on the issues that matter to them."
The Prime Minister's first Queen's Speech included no proposals to curb advertising; a sign that ministers hope to tighten voluntary codes rather than legislate.