East Anglian farming leaders have demanded more than just 'positive words' from Boris Johnson after he vowed to back Britain's 'great farmers' after Brexit.

The prime minister claimed farmers will be boosted by new trade deals and by leaving the EU's common agriculture policy, during a week in which currency markets reacted nervously to the government's ramping up of its no-deal preparations - with the pound falling to a two-year low against the US dollar on Monday.

The National Farmers' Union (NFU) has repeatedly warned of "catastrophic" consequences for agriculture if Britain was to leave the EU without a deal, including potential supply chain disruption, labour shortages and an inability to compete with cheap, lower-quality food imports.

However, Mr Johnson said unless the country was prepared to walk away from the EU without a deal "they won't take us seriously in the course of the negotiations", and that he would make sure the farming sector had the support it needed in that scenario, including "interventions that are aimed to support their incomes".

"I will always back Britain's great farmers and as we leave the EU we need to make sure that Brexit works for them," he said.

"That means scrapping the common agricultural policy and signing new trade deals - our amazing food and farming sector will be ready and waiting to continue selling ever more, not just here but around the world.

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Once we leave the EU on October 31, we will have a historic opportunity to introduce new schemes to support farming - and we will make sure that farmers get a better deal.

"Brexit presents enormous opportunities for our country and it's time we looked to the future with pride and optimism."

NFU East Anglia's regional director Rachel Carrington said the prime minister's positive words were welcome but "what we haven't heard is the detail".

"We need to understand how the government intends to achieve its stated ambitions for Brexit to deliver a better deal for farming," she said.

"Free and frictionless trade with the EU is crucial for farmers across our region. About 60pc of UK food, feed and drink exports are to EU countries and 70pc of our imports in these products were from the EU. The EU is a major supplier for animal vaccines, fertilisers and crop protection products.

"This is not something that can be replaced easily, or quickly, through trade deals with other countries. And trade deals completed in haste run the risk of opening up the UK to food imports produced to lower standards and with lower costs, against which our farmers would struggle to compete."

While meeting farmers in South Wales, Mr Johnson said it was "absolutely vital" for the UK to be ready to walk away from the EU without a Brexit deal.

He said: "Unless we are determined to come out on those terms if we have to - it's up to the EU, this is their call if they want us to do this - unless we are determined to do it they won't take us seriously in the course of the negotiations.

"It's absolutely vital that we are able to walk away."

The prime minister also promised that farmers would have support in the event of a no-deal Brexit making market access "tricky".

"We will make sure that they have the support that they need, if there are markets that are going to be tricky that we help them to find new markets, that we have interventions that are aimed to support them and their incomes," he said.