Like many things considered quintessentially English, the humble strawberry is an immigrant. The first garden variety was grown in France in the 18th century, the result of cross-pollinating strawberries from North and South America. Those luscious fruits you buy today in the supermarket? A marriage of European and A merican strains.

It was only thanks to the penchant of Thomas Wolsey, Henry VIII’s Lord Chancellor, for serving wild strawberries with cream, that the fruit assumed totemic importance in the English psyche, never more so than during Wimbledon fortnight when tennis fans consume more than 34,000 kilos of the stuff.

The good news is that, despite the terrible spring weather, there should be a bumper harvest this summer. A nation breathes a collective sigh of relief. “The crop’s looking very good,” said Nicholas Marston, chairman of British Summer Fruits. “It’s a little later than last year, which, seeing that Wimbledon is a little late, is not a bad thing.”

But the bigger picture in the strawberry fields of Britain this year is far from rosy. Whether growers will have anyone to pick the ripe berries is now a critical issue, one that has profound implications for the UK’s food security, the health of its population and the sustainability of its countryside economy.

“Normally we have 10 people being interviewed by our agency for every job,” said Stephanie Maurel, the chief executive of Concordia which supplies around 10,000 foreign workers to 200 farms in the UK each year.

“As of a month ago we are putting three or four job offers in front of each seasonal worker from Bulgaria and Romania. They are picking and choosing the ones they will come to. There has been a total switch around in 12 months. We’ve never had this before.”

Maurel said some regions would be affected more than others by the shortfall. “It doesn’t hit all farms equally. Scotland suffers a little bit more. There’s a perception that the season is shorter and wetter and it’s therefore more difficult to earn larger amounts of money.”

The temptation is to link the shortage of workers to Brexit. And, certainly, the UK’s decision to leave has not helped matters. “The morning after the vote, we had a pretty depressed workforce,” said Alastair Brooks who grows strawberries and raspberries near Faversham in Kent for supermarkets and employs around 200 Bulgarian and Romanian workers. “There were a few nasty incidents in town. People saying ‘you’ll have to go home now’. It brought out the worst in being British.”

But other factors are at play. “The big problem isn’t so much the referendum as the fact that unemployment in countries like Romania is falling very rapidly,” Marston said. “Clearly, a full-time job in your own country is more attractive than a seasonal job in another country, so the whole pool of seasonal labour within the European Union is reducing annually.”

So, just how acute is the problem?

Evidence submitted by English Apples and Pears Limited to the Department for Food and Rural Affairs (Defra) select committee suggests that almost a third of its members are scaling back as a result of the shortage. Some said they would be removing orchards, a troubling scenario given that more than 60% of the country’s traditional orchards are estimated to have disappeared since the 1950s.

“Urgent action is needed now to avoid crops being left unpicked, food wastage, food inflation and displacement by imported foods,” the submission stated.

The Association of Labour Providers was equally gloomy. It said 49% of labour providers do not expect to be able to source and supply sufficient seasonal agricultural workers this year and added: “Currently an average of 60% of agriculture and horticulture businesses are experiencing shortages in low and unskilled roles, with one in eight in crisis.”

The problem is not confined to fruit picking. The British Meat Processors Association said 71% of labour providers have indicated they will struggle to meet the labour demands of the food manufacturing sector this year.

No one knows just how bad things may become. September, when the soft fruit season ends and the apples and pears season begins, is when demand for labour is at its most acute. In September 2016 the National Farmers’ Union (NFU) said there was a 17% shortfall; in 2017 this had increased to nearly 30%.

The early signs are not reassuring. Data for the first three months of the year suggests the declining trend in labour supply is continuing but it will not be until the crucial May and June figures are published that the true picture will emerge. By then, though, it will be too late.

Afize Yuseinova, right, and her fellow Bulgarians on Langdon Manor farm, are among the dwindling number of European workers happy to stay in Britain. Photograph: Andy Hall/The Observer

“People have got plants in the ground now that they don’t know if they can pick,” Maurel said. “We’ve had a grower go into administration already this year; another has shrunk from nine sites to seven. Farmers are saying they are not going to plant because they don’t know if they can pick. People are writing off fields.”

Last year, Alison Capper, a fruit grower in Worcestershire and chair of the NFU’s horticulture board, had 100 bins of Gala apples that “we just didn’t get to pick in time” due to labour shortages. “With a Gala, the skin goes greasy if it’s not picked in time so we can no longer sell it to supermarkets,” she said. “So they went to an apple juice maker and it cost us £30,000.”

The labour shortage saw labour costs rise by between 9 and 12% last year. A similar rise is predicted this year. “If this continues we will see businesses start to disinvest,” Capper said. “It’s really bad news because fruit and veg is the success story of British agriculture. If we can produce it here it’s going to be of better, nutritional value. Why would we want to diminish our investment in our food chain that delivers the greatest benefit in health terms?”

The roots of the crisis can be traced back to the government’s decision in 2013 to end the Seasonal Agricultural Workers Scheme. Set up after the second world war to help Czech and Polish soldiers who had fought for Britain find work in the country, it has mutated down the years to allow workers from countries such as Belarus, Ukraine and Russia to come to the UK on seasonal visas. At its end, it was confined to Romanian and Bulgarian workers.

Taking the decision to scrap it, the government argued that with Romania and Bulgaria joining the EU there would be no shortage of migrant labour to work on the UK’s farms. Indeed, figures released last week show that there are 2.3 million EU nationals now working in the UK, 2.4% more than there were in the immediate pre-referendum period. More than 400,000 of these are Romanian.

“But we didn’t forsee that the whole of Europe would now be short of people to do this work,” said Brooks whose employees earn in one week what they earn in four back home.

Many of the young, educated, English-speaking workers from eastern Europe have moved on to jobs in other sectors which offer full-time work or to countries such as Germany which are closer to home. In Britain’s fields today seasonal workers from eastern Europe are now more likely to be in their forties, to speak little English and to find picking physically tougher than their younger predecessors.

The situation has become so bad that Concordia is currently recruiting workers from Moldova where a third of the population have Romanian or Bulgarian passports.

Other European countries are bringing in workers from outside the EU. Brooks said Poland was using workers from North Korea while Portugal was relying on migrant labour from Thailand. “Here’s the irony,” Brooks said. “We are the only country in Europe that has a European worker only policy. Everywhere else is recruiting from outside the EU.”

Sunder Katwala, director of the thinktank British Future, said the majority of people accepted that Britain needed to bring in migrant labour if its food supply was to be maintained. “The public recognises that we need to find people to do these jobs if we want our strawberries to be picked,” he said.

“The Seasonal Agricultural Workers Scheme helped fill these vacancies until it was scrapped in 2013. It did the job well and we may need something similar again – a well-managed scheme that brings in the workers we need and makes employers take responsibility for the local impacts of migration, such as on housing.”

But the government appears to be in denial over the issue. In early 2017 it told the Defra committee that foreign labour shortage reports were anecdotal. Then, this February, Defra secretary Michael Gove seemed to signal a volte face, telling an NFU conference a scheme would be announced “shortly”.

The previous home secretary, Amber Rudd, dropped a similar hint, but No 10 is said to be against the plan, perhaps fearing the headlines if it starts issuing visas to non-EU nationals. The fact that prime minister Theresa May was home secretary when the original scheme was scrapped may also be a reason, some growers believe. Few in the horticultural sector now expect anything to happen before the autumn when a government-commissioned report is published and the potential to offer temporary visas to overseas workers can be used as a bargaining chip in Brexit negotiations.

Soft fruit farmer Alistair Brooks, owner of Langdon Manor farm, fears the shortage of workers could be ‘catastrophic’ for his industry. Photograph: Andy Hall/The Observer

A Home Office spokesman defended its position. “The government places great value on the UK’s food and farming industries, both as crucial components of the UK economy and of the fabric of rural Britain. Up until the end of the implementation period in December 2020, employers in these sectors will be free to recruit EU citizens to fill vacancies and those arriving to work will be able to stay in the UK afterwards.”

Capper accused the government of allowing the issue of seasonal workers “to get tied up in the politics of immigration”. “A scheme that brings workers in to pick and pack fruit and veg and them sends them home again has got nothing to do with immigration,” she said.

Maurel said her organisation had been contacted twice last week by Border Force officials asking questions about the workers it was bringing into the UK – “the first time this had happened”.

Brooks said similar questions had been asked of his employees. “We haven’t had this sort of thing in 20 years. You do feel uneasy now as to where we are heading as a nation. We were all deeply shocked and embarrassed by the Windrush scandal but maybe that’s indicative of where the Home Office is.

“If that’s truly the case then that’s a big problem for the UK economy.”

And this is before the UK actually leaves Europe. Some 90,000 workers are needed this summer on UK farms. Of these, 35,000 are on seasonal contracts. “As we get closer to a cliff edge the government say we’re going to have a transition deal but we don’t know that,” Capper said. “If we do crash out of Europe next year I won’t have access to EU workers.”

“That would be a calamity,” said Brooks who is proud of the fact that, during the summer, 99% of Britain’s strawberries and raspberries come from within its shores.

Could UK workers plug the gap? Unlikely. Attempts to recruit them have been “an unmitigated disaster”, Maurel suggested.

“There is no appetite. We ring a bell in the office when a UK worker applies. We put jobs on Jobcentre Plus. Absolutely nothing happens. We’ve had two applications this year in five months.”|

Frustrated by the government’s foot-dragging, some of the big growers have already diversified. One of Britain’s largest berry farmers, Haygrove farm in Herefordshire, announced earlier this year that it was cutting back on its seasonal workforce and expanding in China. Others are investing in South Africa and Tasmania.

For now these growers are outliers. Whether they become the norm will depend on Britain’s ability to secure foreign labour.

Last Friday evening, as she finished her shift picking strawberries at Brooks’s farm in Kent, 27-year-old Afize Yuseinova, was one Bulgarian worker who pledged to continue working here. “I like England,” she said. “There are no jobs for me back home.”

But in the fields of Britain, Yuseinova is becoming an endangered species. Too many countries and industries now want her.

Brooks inspected a strawberry plant and found an ant. He explained that the insect was looking for aphids to milk for their honeydew. But the ant was out of luck as there were no aphids to be found.

“I love Bulgarian workers,” he said. “The problem is there’s only five million of them.”