Tim Farron has accused talkRADIO's Julia Hartley-Brewer of "living in fantasy land" during a clash over the future of food post-Brexit.
The Liberal Democrat MP said it would be "catastrophic" to leave the EU without a deal, and claimed it would result in a 20 per cent increase in food prices.
However, breakfast show host Julia dismissed his predictions, saying food prices were "more likely to go down" under WTO rules.
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"We're not going to put tariffs on foods we don't produce," she argued. "You can keep tariffs on goods that we produce to protect our producers, but don't put tariffs on bananas and pineapples."
"If you think we can double capacity given that we import nearly 50 per cent of the food that we eat in this country, if you think we could double capacity within five years, nevermind five minutes after no-deal, then you really are living in fantasy land," Farron hit back.
'Poverty and hardship'
He added that a no-deal Brexit would result in "enormous poverty and hardship", and hit the poorest hardest.
But host Julia accused the Lib Dem spokesman of "fearmongering", adding: "When that doesn't happen, will you come back on my show and apologise?".
"Yes, of course," Farron replied.