Anyone wanting to understand the economic problems facing Britain in the early 21st century need only consider its national dish.

Chippies are confronting a long list of issues that threaten to send the price of their product rocketing as the holiday season approaches. Brexit, the popularity of online delivery services, freakish weather and concerns about the pollution caused by plastic are all putting pressure on the nation’s 10,500 fish and chip shops.

“I’ve had to hold price increases back so I’m taking quite a hit on things because rival shops are undercutting,” said Andrew Crook, president of the National Federation of Fish Friers. At the moment, a cod and chips at Crook’s chippy in Lancashire costs £5.90, but he intends to put his prices up in the summer.

“I think summer’s a good time to put prices up. People go on holiday, buy fish and chips and see that some areas are more expensive than back home so that does help.”

The drop in the value of the pound since the Brexit referendum means that over the past 12 months it has become 15% to 20% more expensive to import frozen white fish. Higher demand in China, the US and the Middle East for white fish together with cuts in fishing quotas in the North Sea are also contributing factors.

Six months ago a kilo of haddock or cod frozen at sea cost around £4 and £5.20 respectively. Today haddock costs about £5.60 a kilo and cod almost £5.80. There is little respite closer to home. Costs of cooking oil, rent and rates and labour are rising.

Now there is a growing fear that potato prices could soon go the same way. The wet start to the year has delayed the potato planting season. According to Rob Clayton, strategy director for potatoes at the Agriculture & Horticulture Development Board, farmers are between two and four weeks behind where they should be. This could bode ill for the future if the summer turns out to be a damp squib like the spring.

“The holy grail for potato growers is to get the maximum possible leaf cover by the longest day of the year,” Clayton said. “If we were to get a couple of months of warm and sunny weather the problem would go away. If what we end up with is something that’s dull and cool over the next few months then that would retard the development. That is the scenario when you would start to worry about the volume of the crop.” The good news is that there are considerable supplies of potatoes in storage – but these cannot last for ever. “Once you get into August, September that is where those stocks will have run out and the new crop won’t necessarily be as speedy as we thought it was going to be,” Clayton said. “If you’re going to Blackpool in August that’s when you might be expecting a bit of a pinch around chip shop prices.”

Another issue is packaging. Crook said there was pressure on the industry to do away with its polystyrene cartons, which cost around 2p each, and introduce compostable alternatives, made in China, that cost five times as much.

“We don’t think it’s a solution,” Crook said. “It’s been dictated by Blue Planet and the government’s reaction to it. As an industry we try to do the right thing but people don’t know what the right thing is.”

In the 1920s, there were about 35,000 fish and chip shops in Britain. But the number has fallen by two thirds as a huge variety of new cuisines has arrived on the high street. “We’ve been worried for the last 30 years because we’ve had McDonald’s come in and lots of ethnic cuisines and I think people have been scared to put up their prices,” Crook said.

Now the popularity of online delivery services like Deliveroo and Just Eat poses another conundrum. “It’s naive to think deliveries aren’t the way to go,” Crook conceded. “But I don’t think the perfect packaging is there for it right now. With fish and chips you’ve got to keep it crisp. You can’t do five deliveries and come back to base. You’ve got to do each one individually and the margins are not there for that.”