The union's statement follows the publication yesterday of the Government's latest white paper on immigration and asylum.

Pressure from the NFU has already led to the decision to make an additional 3,500 work permits available this year under the Seasonal Agricultural Workers Scheme.

The scheme allows foreign students to work in the UK over the summer, but does not take into account the need for labour in industries which are not at their busiest during the summer months.

NFU chair of employment and education Bob Fiddaman says this scheme is not flexible enough.

'Low unemployment and changes in the rural population and society generally mean we are seeing fewer and fewer people looking for seasonal work,' he said. 'We value student permits, but we need a more flexible green card scheme to plug the labour shortages throughout the industry.' Daffodil growing in south-west England is the latest sector to be hit by the job crisis. It is said that growers were forced to stand by and watch as their harvest withered and died due to a lack of people to pick in the spring.

Poultry farmers, whose busiest period comes later in the year are also expected to suffer this year.