The survey also shows that the number of returning workers to farms, a critical source of the workforce, fell to 16%, its lowest level all year. The returnee rate had been as high as 65% in January.
Farmers are feeling the impact on farm as the cost of food production is rising through higher wages, reduced picking rates and, in some cases, non-harvesting of crops.
The NFU has warned that the supply chain could face significant disruption next year unless government takes immediate action to prevent a shortfall of workers for agriculture.
NFU Deputy President Minette Batters said: “The British horticulture industry is critically important to British agriculture, providing vital jobs and value to the economy.
“As an industry, we have the opportunity to enhance our home-grown food production and increasing the amount of fruit and veg we grow should be a central part of that.
“The situation for farms has become a lot more challenging and farmers are already experiencing the serious effects a lack of workers can have on a business, with some being forced to not harvest crops.
“If the industry continues to see serious shortfalls in the availability of workers, the knock-on effects for the supply chain and the public could be serious.
“Access to a competent and reliable workforce is vital for our food production, especially in a time of record low levels of UK unemployment.
“There remains a window of time between now and May 2018 for the government to take action to prevent a shortfall and the ensuing impacts.
"The simplest measure would be a tried and tested seasonal agricultural workers scheme open to non-EU workers to top-up the access we have now to EU nationals.
“Post-Brexit, we need to see an immigration policy that is based on fact and business need and recognises the importance and seasonality of workers across all skill levels.”