NFU deputy president Tom Bradshaw said a reliance on imports has left the UK vulnerable to "shock weather events".
Soaring energy bills exacerbated by the war in Ukraine have also put off some UK vegetable growers, he added.
He said the UK has now "hit a tipping point" and needs to "take command of the food we produce" amid "volatility around the world" caused by the war in Europe and climate change.
It comes as the shortage of tomatoes in UK supermarkets has widened to other fruit and vegetables due to a combination of bad weather and transport problems in Africa and Europe.
Mr Bradshaw told Times Radio on Saturday: "We've been warning about this moment for the past year.
"The tragic events in Ukraine have driven inflation, particularly energy inflation to levels that we haven't seen before.
"There's a lack of confidence from the growers that they're going to get the returns that justify planting their glasshouses, and at the moment we've got a lot of glasshouses that would be growing the tomatoes, peppers, cucumbers, aubergine that are sitting there empty because they simply couldn't take the risk to plant them with the crops, not thinking they'd get the returns from the marketplace.
"And with them being completely reliant on imports - we'd always have some imports - but we've been completely reliant on imports (now). And when there's been some shock weather events in Morocco and Spain, it's meant that we've had these shortages.
"It's really interesting that before Brexit we didn't used to source anything, or very little, from Morocco but we've been forced to go further afield and now these climatic shocks becoming more prevalent have had a real impact on the food available on our shelves today."
On Wednesday, Tesco followed Aldi, Asda and Morrisons in introducing customer limits on certain fresh produce as shortages left supermarket shelves bare.
Tesco and Aldi are limiting customers to three units of tomatoes, peppers and cucumbers as a precautionary measure, while Asda is also limiting customers on lettuce, salad bags, broccoli, cauliflower and raspberries, and Morrisons has set a limit of two items per customer across tomatoes, cucumbers, lettuce and peppers.
Retailers believe the problems stem from poor yields on the continent and north Africa, and that supplies will improve in the coming days or weeks.
Environment Secretary Therese Coffey said on Thursday that British consumers should eat more turnips instead of imported food.
Growers have also warned that a leek shortage will see British-grown supplies exhausted by April, with high temperatures and a lack of rain, followed by a period of cold weather, blamed.
Jack Ward, chief executive of the British Growers Association (BGA), has reportedly said supermarkets could also experience shortages of carrots, cabbage and cauliflower within weeks.
The BGA has also warned that the future of British apple and pear-growing is "on a knife edge".
A BGA survey of British Apples & Pears Limited (BAPL) members, which represent an estimated 80% of the UK industry, found 150,000 orders for new apple and pear trees - a third of the planned 480,000 - have been cancelled this season.