It has long been a puzzle why organisations such as Amnesty International, Greenpeace and Friends of the Earth cannot become charities. Opinion polls show the public already think they are, but decades-old rules that limit the amount of campaigning charities can do, and place even greater restrictions on political activity, prevent it.

However, that could be about to change, enabling dozens of campaigning organisations to win charitable status, along with the valuable tax breaks and fundraising opportunities that come with it.

Firstly, the Charity Commission has decided to scrap guidelines that have restricted the campaigning activities of charities. Dame Suzi Leather, the chairman of the Commission, has argued that the current guidelines are not helpful and not clear and potentially discriminate against smaller charities which want to campaign but have not enough money to fund wider charitable activities in order to justify it.

Last week, the Commission drew up plans to allow charities to spend their entire time campaigning if they want to. Dame Suzi has told trustees that if they believe the organisation can best further its aims and those of its beneficiaries by campaigning full-time, “it is fine by us”.

That is a step in the right direction, as far as the campaign groups are concerned, but on its own not enough to allow Amnesty and Greenpeace into the charity tent. There are still heavy restrictions placed on political activity that stand in the way.

Existing charities may carry out “political activity”, but only if it furthers its charitable purpose, and organisations with “political purposes” cannot be charities. The definition of “political” in the law is broad. Activity is judged as political if it attempts to secure a change in law or policies of a government, in the UK or abroad.

The Charity Commission feels the effect of changing the definition could be so great that more thought needs to go into it. It has launched a debate. Although officially agnostic, the Commission is concerned that narrowing the definition to, say, simply ban partypolitical campaigning could compromise public trust in charities.

However a head of steam is now building up around the issue. In May, the Advisory Group on Campaigning and the Voluntary Sector, chaired by Baroness Helena Kennedy, QC, said there should be no restriction on the amount of political campaigning charities can do. Some ministers also believe a liberalisation of the law could give a boost to political campaign groups and single-issue causes which would help reconnect the public with the political process.

Last week, a coalition of voluntary organisations began to lobby for an amendment to charity law that would allow registered charities to dedicate all their resources to political campaigning, though it would keep the ban on explicitly political organisations becoming charities.

That change could be enough for organisations such as Amnesty to win charitable status. It feels particularly hard done by as its core activity — promoting human rights — has been deemed a charitable act by Parliament.

Amnesty has welcomed the decision of the Charity Commission to change its guidelines, but said a change in the law was required to level the playing field.

“We welcome the proposal to change the guidelines. But we think the whole thing needs a change in the law rather than just in guidelines,” said Melvin Coleman, the company secretary at Amnesty International UK. “You can't go very far in promoting human rights, which has been deemed a charitable purpose, before you need to campaign to change law or policy. We think the government is sympathetic and hope this can be resolved.”

The National Council for Voluntary Organisations (NCVO), which represents all charities, said it, too, was pleased the confusion on campaigning was going to be cleared up by the Commission and urged debate on the more controversial aspects of the law on political campaigning.

“This has cause a lot confusion for charities over how they can operate. Scrapping the dominance qualification sounds like something charities can actually get their head around,” said Belinda Pretton, the head of policy at NVCO.

“But we would also welcome a debate on the definition of political campaigning. There is a growing recognition that getting people interested in issues and making sure a range of views are heard is very important in a democracy, although getting the balance right in terms of retaining public trust in charities is also very important.”

The Countryside Alliance said the current law was inconsistent an should be changed.

“There should be a level playing field. We always thought it was very unfair that charities were allowed to campaign heavily for a hunting ban and use their resources to run ads, while we would have been shown the door if we applied for charitable status,” said Tim Bonner, spokesman for the organsation.

However, the Countryside Alliance has set up a foundation to pursue educational work in schools, and between towns and country, and is now in the process of seeking charitable status.