Britain is in the grip of a courgette shortage that could last for months after a continental cold and wet snap hit supplies at a time of peak demand from consumers keen to pursue new year resolutions to eat more greens.

Wholesale prices for courgettes, a staple of the Mediterranean diet, have more than tripled after unusually cold and wet weather in Spain where most of the European supplies are grown.

Consumers across the UK, many of whom are keen to pursue healthier diets, have complained on social media about a lack of courgettes in supermarkets and online retailers.

Jordi Vorderman, the UK sales manager at Dutch vegetable supplier Valstar Holland, said prices had quadrupled since the summer. He said: “The main issue is that supplies are low because of cold nights in Spain and Italy. The cold affects courgettes a lot.”

He speculated that some UK supermarkets were not prepared to buy courgettes at such inflated prices. “Prices are very high – they are above £20 for a 5kg box. So what retailers are probably doing is that they are not buying at these prices and would rather go empty in the stores than buy at these silly levels. During the summer prices are between £4 and £6.”

“Everybody in January tries to eat a more healthy diet, but the real problem is supply. And it’s not just courgettes. Lots of prices are extraordinarily high – peppers, aubergines, tomatoes.”

Colin Putt, sales manager at the vegetable supplier Total Produce, warned that vegetable shortages could last for months as growers in Spain struggle to recover from the weather.

“I’ve never seen it so bad on so many products. It’s not just courgettes, it’s most of the produce we get from Spain at this time of the year. They had a year’s worth of rain in less than 24 hours, and they’ve cold weather as well.

“One of our growers in Spain has lost over 5m heads of lettuce. And because of the weather they can’t replant.”

The problem has been made worse by an increase in demand. Putt said: “You get more of an uptake in demand at this time of year because of healthy fad diets.

“I think it is going to last for a while. The growers are saying they’ll have another look in two or three weeks, but I just think it will be a lot longer than that. I can’t see how they can turn round the volume required.

“We also get courgettes from Morocco at the time of year but they’ve had bad weather as well. And Morocco doesn’t grow the volumes to cover the shortfall.”

He said courgette wholesale prices were at least triple the normal levels for this time of year.

“Most places we are being quoted over £20 a box for a 5kg box and that’s if they’ve got any. This time of year you would normally get boxes for £6 or £7.”

The weather has forced growers to pull out of fixed price agreements, Putt added. He said: “Usually they give us prices in September that will go right through to April. Because of the weather they are citing force majeure and have to pull out of the programme.

“So supply has dried up. A lot of supermarkets get fixed prices but if the product is not there they can’t supply it.”

Char, a fashion student, tweeted about her struggle to find courgettes in West Yorkshire.

And those keen to eat “courgetti” – where the vegetable is cut into thin ribbons to provide a low-carb alternative to spaghetti – have also found shelves bare.

Supermarkets acknowledged there were supply issues. A Tesco spokesperson said: “Due to bad weather conditions in Spain, we are experiencing a few availability issues, but are working with our suppliers to resolve them as quickly as possible.”

A Sainsbury’s spokesperson said: “There has been severe weather in southern Europe but we are working with our suppliers to maintain supply for our customers.”