It is a strange and surprising day when the Prime Minister decides to say something about our land use planning system.

But Mr Cameron's intervention yesterday was welcome. None of us (including the National Trust) is interested in a game of brinkmanship. We want to find a way through this mess and we now have the opportunity to do just that.

So, we have offered the Government the terms of negotiation and talks will resume!

One thing that we will be seeking clarity on is the fate of England's finest wildlife sites - Sites of Special Scientific Interest. We were uncertain about how the National Planning Policy Framework would affect SSSIs and so we sought legal advice. The advice, which we have now shared with the Government, essentially concludes that those SSSIs which do not underpin internationally designated sites will be more vulnerable under the NPPF as currently drafted.

The current system essentially advises local authorities to reject development that damages SSSIs unless the benefits of the development outweigh the negative impacts. Under the proposed new system, local authorities will be obliged to consent development "unless the adverse impacts of allowing the development would significantly and demonstrably outweigh the benefits".

We therefore do not think that the Prime Minister was right when he stood up in the House of Commons last week and said that protection for SSSIs was unaffected by the draft NPPF proposals.

Now I know what you are thinking - that lawyers can often give you the answer you want to the question you set.  Yet, I think that saying SSSI protection has not changed is akin to saying that the presumption of innocence until proven guilty is the same as the presumption of guilt until proven innocent.

These are not semantic points. The RSPB knows from experience how the words in the new planning policy will be used by developers and lawyers. We want assurances through the redrafting of the NPPF that SSSI protection remains as strong as it is under the current system. Anything less would seriously undermine this government's credentials of seeking to "protect wildlife and ... restore biodiversity".

We look forward to continuing our conversations with ministers and officials...