WE NEED to sort out our incoherent attitude towards migrant workers if Britain is to feed itself. Currently, the disconnect is blatant. Have you seen the UK Borders Agency's TV advert? It would leave you in no doubt that the UK government is taking a tougher line on immigration.

The tone is sinister, a pounding heartbeat redolent of a horror film and a threatening voice-over. Ostensibly it is aimed at those who want to sponsor migrant workers: "Get a licence or you won't get through the immigration hurdles." But it plays to the wings too, with a nasty little subliminal message to the general public: "Look what your government is doing to keep foreigners out."

This is not just reactionary, it's dangerous. The truth is that far from being over-run by migrant workers, we're running out of them. This season, fruit has rotted and vegetables have been ploughed back into fields because the UK government won't allow in enough people from outside the European Economic Area to pick them. UK-wide, it has already cut the number of legal entries through the Seasonal Migrant Workers' Scheme (SWAS) from 25,000 to 16,000.

By 2010 it intends to phase out the programme, which gave work permits to foreign workers for a fixed period to help us harvest.

This year, only Romanians and Bulgarians qualified for the scheme. The result? A drastic shortage of labour (about a third fewer pickers than were needed) and an average loss to growers up and down the land of £140,000 in just one season.

This crackdown on foreign labour is folly. British horticulture is in a bad state anyway. At a time of world shortage, when every prudent country should be building up its self-sufficiency in food as a buffer against rising fuel and food prices, the UK is highly vulnerable, growing only 10% of the fruit and just over half of the vegetables we eat. So we ought to be encouraging growers, not making it harder for them to survive.

Be in no doubt, it is migrant labour that has kept British horticulture going for the last 20-30 years. Foremost among them in Scotland, Gypsies or travellers and foreign students earning money during their holidays. Lately, we've seen gangmasters taking advantage of the labour shortage by supplying workers, many of whom lack the requisite permits.

Cut all that crap about foreigners coming and stealing "our" jobs. Locals haven't been doing the berry picking and tattie howking for decades. There seems to be some universal law that as societies become more affluent, fewer people want those hard, manual jobs in the fields, so it's migrant workers from poorer countries who step in. That's why Nicaraguans pick the citrus groves of Costa Rica and why Haitians cut sugar cane in the West Indies.

Seasonal migrant pickers do unglamorous, often poorly paid, temporary jobs that the locals won't or can't do. Most native job seekers are looking for permanent positions, and our indigenous unemployed, who might be incentivised into seasonal picking work, currently lose their state benefits if they take up this work.

Horticulture suffers from an image problem too. Culturally, we make the mistake of seeing work on the land as backward and low status. We need to get back to thinking of it as we did in the second world war, when our food supply was being choked off by German U-boats and farmers and growers were seen as vital pillars of society, keeping the population from starvation.

The UK government can play all it likes to the xenophobes, the racists and Little Englanders, but it is screwing up our food production in the process. What it should instead do is make it easy for both our own unemployed, and people from outwith the European Economic Area to work in our fields. It needs to stamp out the exploitation of illegal migrants by the more unscrupulous gangmasters by relaxing immigration controls and making it more straightforward to come to the UK for seasonal work.

But Gordon Brown's government is so keen to be seen to be talking tough on immigration that the Home Office is turning a deaf ear to the 999 calls from farmers and growers.

Retrospectively, when the worsening figures illustrating Britain's growing food trade deficit with the rest of the world end up on ministers' desks, they might think better of it, but by then it will be too late.

British growers have been hopeless at making their concerns known. They would do well to take a leaf out of the book of the Indian restaurateurs who recently took to the streets of Glasgow and London to protest against the new immigration measures that prevented them from recruiting chefs from the Indian subcontinent.

The Home Office subsequently revised its list of occupations and skills that are in short supply in UK to enable employers to recruit skilled chefs from outside the European Union.

Or why not take some French farmer-style direct action? Perhaps some rotting berries and pungent brassicas dumped outside Downing Street along with this simple message: "Migrant workers? Bring them in. Lots of them. We need them."