A rise in the price of wheat after an unusually small harvest will add around £20,000 a week to the costs of major bakeries and could affect the price of bread in shops, it has been claimed.
And the head of one of Northern Ireland's biggest bread makers has warned that a no-deal Brexit could also compound inflationary pressures on flour and bread.
Brian Irwin, chairman of Irwin's Bakery, said: "I've been in the food trade for 40 or more years, and we've had a really small harvest this year in the UK - the smallest in 40 years - and that's alarming.
"Food production as a whole industry across the board exists on very slim margins, and within the food industry bakeries probably exist on thinnest of all margins. It's not in a great place for absorbing massive price increases."
He said a wet autumn had held farmers in Britain back from getting planting done for their winter wheats.
And while there had been a dry spring, the grain was not "plumped up" enough to make for a good harvest.
"That scarcity drives up prices, and it means that the UK has been importing more German wheats to make up for the overall shortage," he explained.
"The value of sterling has gone down, particularly with the rather pessimistic projections on the economy, and more particularly Brexit. So, with the pound down, German wheats are more expensive."
He said that importing wheat would add £1m a year to a bakery's costs - around £20,000 a week. And the price of flour was up by around 30% as a result of the increasing price of wheat. But he said retailers would remain in control of the price of a loaf of bread.
He added: "It's inevitable there will be inflationary pressure on bread. That will work its way into the consumer basket."
However, he said it would be affordable: "As a historical observation, we've seen bread prices move one year to the next by amounts of 5p or 10p."
Mr Irwin warned that without a Brexit deal a tariff on German wheat could add to the rising costs.
He said: “Without a deal, the German wheat making up the shortfall will be subject to a tariff of £79 a tonne that would be a 40% increase. That’s on top of the current high prices of wheats for milling anyway, and that’s a big concern.”
Irwins employs around 360 people in the production of breads including Nutty Krust, wheaten, Veda and the Rankin’s Selection. It also makes baked goods under the Howell’s brand.