NFU President Meurig Raymond opened the NFU's national conference on Tuesday by declaring the forthcoming election as "one of the most important we have ever faced".

And he said there was no doubt that food and farming were key electoral issues.

Research from the NFU released ahead of the conference suggested the UK's self sufficiency is in a 30-year downward spiral, with 60 per cent of food needs met with produce from farms here, compared to more than 80 per cent in 1984.

With the UK population expected to grow to 70 million in 20 years, the figure could fall to 53 per cent by the 2040s, having serious implications for the British economy, food security and employment.

Mr Raymond told the conference that an independent YouGov survey commissioned by the NFU showed 85 per cent of British people want supermarkets to sell more British food.

"The same survey shows that nearly eight out of 10 people believe the government should do more to ensure a secure and affordable supply of British food," he said, "That clear message from British people must be taken on board by the next government."

Mr Raymond also said government has a duty to tackle market volatility which was fast becoming the norm.

"The mechanisms we used to see to ensure stability have been dismantled: quotas for milk end this year and for sugar in 2017," he said. "Tariffs have come down and there are an unprecedented number of trade deals on the table that will expose European producers to further competition.

"Export refunds are no longer used and intervention, where it exists, is at a minimal level. So, we need to find other ways to manage price volatility."

The next government could help by ensuring the food chain works correctly; providing unhindered access to futures markets; longer periods for tax averaging; better labelling regulation; the removal of barriers to diversification and more exports.

He also called on retailers to commit to longer term contracts and relationships.