The appeal by Animal Defenders International against the ban imposed on its My Mate's a Primate advertisement will be heard in the House of Lords next week. If the campaigning group succeeds in overturning the ban, it will set a legal precedent that will pave the way for other NGOs to advertise on television for the first time since the 2003 Communications Act came into force, providing a significant and powerful addition to their campaigning armoury.
But when ADI produced the advert to highlight the four main threats facing primates, little did Jan Creamer, the organisation's chief executive, realise what she was getting into. The advert was banned in March 2006, and it has been campaigning to overturn the decision ever since.
"We actually redesigned the ad to comply with all the regulations," says Creamer. "But then the Broadcast Advertising Clearance Centre banned it, not because of the content, but because of who we are - we're deemed to be a 'political group' under the 2003 Communications Act.
"We thought that was incredibly unfair, because wealthy corporates can spend millions on pumping up their own image on television - so we decided we had to appeal."
For a small organisation such as ADI, the potential cost was a big issue. It has had no financial help from the rest of the sector, even though thousands of organisations stand to benefit if it is successful.
"I understand that it's a difficult decision to allocate funds to something like this," says Creamer. "Giving money to lawyers is never going to be popular with supporters."
Creamer is optimistic about the case, and believes the report by the Advisory Group on Campaigning and the Voluntary Sector, chaired by Baroness Kennedy, has helped create a favourable climate for the hearing.
She is broadly supportive of the report's findings and the group's call for the law to be changed to allow charities to dedicate all their resources to campaigning.
"There's been a shift in public opinion," she says. "People can see the logic behind allowing charities to campaign."
Creamer dismisses as nonsense the argument made by Greg Clark, the shadow charities minister, that such a change would knock public confidence in charities.
"I don't think people make the distinction between charities and campaigning groups," she says. "They are more interested in the work that's done. We have to get away from this habit of thinking the public needs to be protected. It's rather patronising."
But even if the Kennedy group succeeds in its aims, Creamer believes ADI would still have to consider carefully whether applying for charitable status would be worth its while.
"It could stop us being totally effective in terms of campaigning," she says. "Charity law tries to separate politics from society, but it's an artificial distinction.
"Our supporters already see us as a charity in all but name. Our work is charitable - we organise animal rescues, fund research and educate."
ADI shares a Westminster office with its sister organisations the National Anti-Vivisection Society and the Lord Dowding Fund, of which Creamer is also chief executive. The former was a charity until 1947, when a landmark judgement stated that it could not be a charity because it existed primarily to change the law.
"We think the law is wrong," says Creamer. "You can raise money to try to alleviate suffering, but you cannot change the law to prevent the suffering. It seems it's OK for us as a sector to sweep up after society, but we can't take steps to stop things happening."
1990: Co-founder and chief executive, Animal Defenders International
1986: Chief executive, NAVS and the Lord Dowding Fund for Humane Research
1982: Editor, The Campaigner and Animals' Defender, National Anti-Vivisection Society
1978: Sales and marketing executive, Landor Associates.