But they said the night-time swoops were difficult to stop and they were appealing for farmers to watch their crops in the crucial lead-up to harvest.

A Police spokesman said: "We believe it is one guy. We've had several reports from Somerset to the East End. The way they have been done is very similar.

"But whomever is doing it has several helpers -- it's not just one guy filling his pockets.'' She said the thefts were seasonal, with cases rising over the winter months.

"Investigations are underway but these thefts are a one-off thing. They can only take the produce when it is ripe so it would behove farmers to be extra vigilant at that time,'' she said.

Farmer Tom Wadson said: "It's a big problem. It's wholesale theft. It's going on around the Island. It seems to be getting worse.

"This stuff isn't going out in a shopping bag, it's going out in a cattle truck.'' He called on buyers to ask questions about where goods had come from.

He said: "If you are not buying from a regular grower, you run the risk of getting caught with stolen goods if you don't have a receipt.

"These guys are very professional. They are obviously watching the crop until it's ready.

"They are taking anything and everything, pumpkins, tomatoes, broccoli, cabbages.'' And he was angry that some people thought that it was okay to take crops because they were seen as a natural product.

He said: "I caught one Rasta stealing who said it was okay to take it because God grew it. I told him God was going to bust his a** for stealing.

"Only a six-year-old child could think this way.

"It doesn't matter if it is a TV or a tomato, you are stealing.

"If I catch anyone, they will suffer the full extent of the law.

"I wouldn't want to be a guy who got caught in a farmer's field the way they are feeling about this.'' The Police spokeswoman said farmers should invest in fences and guard dogs to protect their property while neighbourhood watch schemes could help some farmers.