Former prime minister Gordon Brown has called for a no-deal Brexit to be stopped "in its tracks" as he warned of the consequences on a visit to a Liverpool bakery.
The former Labour leader visited the Homebaked co-operative bakery in Anfield on Monday but warned poverty in the area could get worse if Britain leaves the European Union with no deal.
He joined the GMB union, campaign group Hope Not Hate and food charity Sustain in writing a letter to warn Prime Minister Boris Johnson that crashing out of the EU threatened food supplies.
Mr Brown said: "Jobs are affected, health is affected, the supply of food is affected and any Government that is responsible, if they cannot give a guarantee of uninterrupted supplies, if there is a risk, then they should not be proposing a no-deal Brexit."
Michael Gove, the Cabinet minister charged with no-deal preparations, admitted some food prices could go up in a no-deal scenario.
Speaking on the BBC's Andrew Marr Show on Sunday, Mr Gove said: "Everyone will have the food they need."
Asked if food prices would increase, Mr Gove said: "I think that there are a number of economic factors in play. Some prices may go up. Other prices will come down."
Mr Brown said: "To stop a no-deal Brexit is important because poverty otherwise will get worse, food prices will go up, fuel prices will go up and therefore people's cost of living will be affected and, of course, people who are giving money to food banks will find it more difficult to do so because they themselves will be under pressure.
"We have got to stop a no-deal Brexit in its tracks."
Mr Gove had also said "there will be no shortages of fresh food" if the UK leaves the EU without a deal.
But the trade body for UK retailers said this was "categorically untrue" that such supplies would be unaffected in a no-deal Brexit scenario.
Responding to Mr Gove's claim, a spokesman for the British Retail Consortium said it is "impossible to mitigate it fully as neither retailers nor consumers can stockpile fresh foods".
Angela McKay, operations manager at the Homebaked bakery, said they had already seen the prices of their supplies going up.
She said she thought some politicians were "too removed" from communities like Anfield to make decisions on the future of the country.
And she added: "They don't understand, or they do understand but just don't care, the consequences it will have on people further down the line.
"We're employing 20 people, if people don't come through the doors because we've got to put our prices up we could have to lose staff. That's not something we want to do."
GMB general secretary Tim Roache said: "With no deal, we're likely to see a huge impact on everything from increased cost of the family shop and less choice on supermarket shelves, through to job losses in food production and reduced nutrition in school and hospital meals.
"The Government are walking us to a cliff edge and seem more interested in ideological Tory Party politicking than making sure we have a stable food supply."
Mr Brown also said the Government would be bound to follow legislation blocking a no-deal, if it was passed by Parliament, or there would be "major consequences" for democracy.
He said: "We were told that we were leaving the European Union to uphold parliamentary sovereignty and if the Government themselves are prepared to abandon parliamentary sovereignty in the interests of their own ideology or their own dogma then I think most people round the country would see that as a constitutional outrage."