Fiona Reynolds, director-general of the National Trust, is unapologetic about challenging the government so publicly on the proposed changes to the planning laws. More than 100,000 people have signed the trust's petition, and there have been angry reactions from ministers, especially the planning minister, Greg Clark.
"This campaign is very unusual in many ways," says Reynolds. "But it goes back to the fact that during the 1920s and 30s the trust played a pivotal role in the establishment of the land-use planning system.
"We've relied on a planning system to do the job that in some ways the National Trust was created to do. When there's a threat to the planning system, we do feel very clearly that it is right for us to stand up to it.
"It's not a political campaign in any shape or form - it's a policy campaign based on some really strong concerns about what appears to be a major change of policy that will diminish protection for the countryside and historic places."
The trust, with about 3.9 million members, is the country's largest membership charity. But were the members consulted about the campaign? "It's really important to remind people that our accountability is to the nation and not to our members," says Reynolds. "Our statute is very clear that our members support the National Trust, but our accountability is that we exist on behalf of the nation as a whole," she says. "We are a large organisation, but the points that we have been making have been from the trust's perspective and not on behalf of our millions of members."
The trust has been careful to ensure that the majority of its members are behind the campaign, but Reynolds concedes that there are some who are "less enthusiastic" about its stance. She adds it was never the trust's intention to have such a public dispute with government ministers.
"I do think that the ministers who made some very provocative remarks over the summer have a lot to do with how this issue became a lot more visible. If they had responded calmly and constructively, we might have been in a very different position. Some of those remarks weren't helpful - the press focused on those and elevated the issue."
She also understands the position of other charities - such as Shelter - that have publicly come out in favour of an overhaul of the existing planning regulations to make it easier to build more affordable homes. "We have every sympathy for the need to provide housing in the right place," says Reynolds. "We make no bones about the fact that we recognise the planning system needs to change. The question is whether this proposal will deliver what people want - we don't think it will."
Read our analysis on charity campaigning