A row has broken out between the CLA and the government over lack of representation in trade talks.
It follows the publication on Friday of a Department Of International Trade document showing portfolio responsibilities for Secretary of State Liam Fox and his three ministers.
There is no mention anywhere of agriculture or food.
By Monday morning the CLA jointly with Scottish Land and Estates had hit back warning the failure to secure strong trade opportunities for agricultural products would put UK food security and the environment at risk.
The organisations say their complaints come in the context of agriculture being historically treated either as a low priority or excluded from international trade negotiations altogether.
CLA Director General Helen Woolley said: "Leaving the EU can be an opportunity for businesses across the countryside. If the conditions are right we will thrive. But those conditions will not come about without careful planning and tough negotiations.
"Nowhere is that more the case than in agriculture. It is notoriously difficult to establish open trade deals for farming products. It is seriously alarming that no Government Minister has been given specific responsibility to deliver it.
"We now seek urgent reassurance that Government will deliver for our farmers and rural producers. We expect the Department for International Trade to start working together with us straight away and this is a terrible start. The nation’s food security may be compromised. The environment could start to suffer and many farms and manufacturers could go out of business.
A Department for International Trade spokesman however insisted later on Monday that the CLA and SLE were mistaken and that Mark Garnier MP, one of Dr Fox’s three strong ministerial team was in fact to take responsibility for agriculture.
This however was not reflected in the DIT website which gave Mr Garnier’s responsibilities as financial services, advanced manufacturing and aerospace, automotive industries, the bio-economy and consumer, creative and education interests.
There was no mention of food or agriculture anywhere in the portfolio.