A farming minister is on a campaign collision course with the environment secretary after outlining his reasons for wanting to leave the European Union (EU) during a speech in Norwich.

George Eustice’s decision to join the “leave” camp will put him on the opposite side of the referendum debate to his boss, Environment secretary and South West Norfolk MP Elizabeth Truss, who has declared her support for the campaign to remain in the EU.

While speaking at a scientific conference at the John Innes Centre in Colney yesterday, Mr Eustice said Britain would have more control over agricultural policy, budget and regulation if it was freed from the constraints of EU law.

He said: “I’ve reluctantly come to the conclusion that the only way to get the sort of radical reform we need in the UK is to leave the EU and replace our membership of the union with a new UK-EU partnership.

“From my own point of view, we would replace the CAP (Common Agricultural Policy) with a British agricultural policy that would be properly funded. But we might spend money in different areas We might be more focused on science and technology and knowledge transfer and we might put greater emphasis on risk management tools and insurance schemes.

“Fundamentally, because we would we running our own policy, funded by ourselves, it gives us freedom to develop the kind of kind of policies we want, without always being second-guessed by auditors in the EU.”

When asked whether spending on agricultural support would be threatened by the pressures on public funding in the UK, Mr Eustice said: “I don’t think it will happen. There is an understanding of the importance of agriculture in this country and people recognise that we need to support our farming industry and protect our environment.

“So I don’t buy into this ‘Armageddon’ idea that there will be no money at all. You can spend money differently, you can spend it more wisely, more effectively – but there would be continued support for agriculture and the environment.”

The government had previously been criticised by farmers for refusing to discuss its “Plan B” in the event of Britain leaving the EU, in important areas for the industry such as subsidies, trade relations, chemical regulation and access to labour markets.

Now, following Mr Eustice’s declaration at the Norfolk Farming Conference two weeks ago that the onus would be on “leave” campaigners to explain what post-Brexit policy would look like, farmers are looking to him to provide the detail.

Robert Sheasby, regional director for the National Farmers’ Union (NFU) in East Anglia, said: “Having listened to George Eustice today, I remain concerned at the lack of detail behind his statement that support for agriculture would probably remain, as well as there being money available for the environment and research and development.

“At the moment we seem to be long on rhetoric and short on hard facts from both sides in this debate about the benefits and disadvantages of EU membership for British farmers.”

Mr Eustice said there would be no friction at the Department for the Environment, Food and Rural Affairs with Ms Truss, who said she backs the “remain” campaign because “it is in Britain’s economic interest and means that we can focus on vital economic and social reform at home.”

“There is no tension whatsoever between different members of the government,” said Mr Eustice. “We all have respect for each other’s position.”